The Glossary of Industry terms has been compiled by SAAMI’s Technical Committee to facilitate technical interchanges between members of that committee. It is not intended to provide legal definitions of the terms included, and, in light of further experience, the definitions of these terms may change. It is not intended to be comprehensive since it does not cover the full range of the diversity of the sporting arms and ammunition industry’s products. It is, in other words, a working draft that, it is hoped, may be useful in addressing certain technical matters frequently considered by the Technical Committee and is subject to further change and refinement.
It was the committee’s decision that ONLY industry terms would be included which are unique to the firearms and ammunition industry directly. Optical terms have been omitted for the most part. Common metallurgical terms were not included because they are not unique to the industry. Where there is a common term with a usage unique to our industry, it has, however, been included.
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ACCELERATOR
A device found in some semiautomatic firearms that, through mechanical advantage or spring energy, transfers kinetic energy from one part of the mechanism to another with the resultant speeding up of the action.
ACCURACY
In firearms using single projectiles at a given distance, is the measure of the dispersion of the group of projectiles fired. The optimum would be one hole no larger in diameter than a single projectile. See Mean Radius.
Related Terms: MEAN RADIUS
ACCURACY LIFE
An estimated, or empirically determined, number of rounds that can be fired in a particular gun, of a particular caliber, before it fails to meet a particular accuracy specification. Wide variations may occur due to caliber, ammunition characteristics, firing schedules, maintenance and firearm design.
ACCURIZE
The act of subjecting a firearm and its components to special fitting and operations with the goal of optimizing accuracy.
ACTION
The combination of the receiver or frame together with the other parts of the mechanism by which a firearm is loaded, fired and unloaded.
ACTION BAR FLATS
Formed or machined surfaces on the action bars which control or actuate, through cams or blocks, the movement of other parts of the firearm as the bars move in a reciprocal motion.
Also Known As: Action Bar(s)
Related Terms: ACTION BAR(S)
ACTION BAR(S)
A member or members, which are used to connect and, thus transmit the movement of the forearm or gas system to the breech block. In many designs, the movement of the action bars controls or actuates other parts of the mechanism.
Also Known As: Action Bar Flats
Related Terms: ACTION BAR FLATS
ACTUATOR
Part of the firing mechanism in certain automatic firearms, such as trigger actuator, which slides forward and back in preparing each round to be fired.
ADJUSTABLE SIGHT
Usually taken to mean a rear sight that is adjustable for windage or elevation or both. However, adjustable front sights are sometimes used on target firearms.
ADJUSTABLE TRIGGER
Any trigger mechanism which has features that can be adjusted.
AIM
The act of aligning a firearm on a target.
AIMING POINT
A point on the target upon which the firearm is aimed.
AIR GAUGE
A pneumatic device for measuring diameters.
AIR GUN
A gun that uses compressed air or gas (e.g. carbon dioxide) to propel a projectile. Technical standards for air guns do not fall under the purview of the Sporting Arms and Manufacturers’ Institute.
Also Known As: Air Rifle
AIR PISTOL
A handgun with the same principle of operation as an air gun. Also called Pellet Pistol. See Air Gun.
Also Known As: Pellet Pistol
Related Terms: AIR GUN
AIR RESISTANCE
The resistance of air to the passage of a projectile in flight.
AIR SPACE
The volume in a loaded cartridge or shotshell not occupied by the propellant or the bullet, wads or shot. Sometimes called Ullage.
Also Known As: Ullage
AIR SPIRAL
The term used to describe the corkscrew-like flight path of a bullet.
ALTITUDE EFFECT
The effect on velocity and, therefore, trajectory and shotshell pattern caused by changes in atmospheric density due to altitude.
AMMUNITION
One or more loaded cartridges consisting of a primed case, propellant and with or without one or more projectiles.
AMMUNITION CODE NUMBER
A code number and/or letter(s) usually found on the carton that identifies a particular quantity of ammunition for its manufacturer.
AMMUNITION COLOR CODE
A method of distinguishing various gauges of shotshells and types of metallic ammunition by color or plating.
AMMUNITION LOT
A continuously produced batch of ammunition uniquely identified by a code. Lot size is determined by the manufacturer as part of their manufacturing process.
ANGLE OF DEPARTURE
The angle formed between a horizontal line and the center line of the bore at the moment the projectile leaves the muzzle of the gun.
ANGLE OF ELEVATION
The vertical angle formed between the line of sight to the target and the axis of the barrel bore.
ANNULUS
The ring-like space between the top of the primer and the primer pocket or battery cup on the base of a cartridge.
ANSON FASTENING FORE-END
A fastening method of the fore-end of double barreled shotguns which utilizes a spring loaded bolt that extends beyond the tip of the fore-end. A British term.
ANTIMONY
A metallic element used to alloy lead to increase hardness. Symbol Sb.
ANVIL
An internal metal component in a cartridge primer assembly against which the priming mixture is pinched by the firing pin blow. See Primer.
Related Terms: PRIMER
APERTURE SIGHT
A form of metallic sight, front or rear, containing and aperture or disc with a hole. Also called Peep Sight, or Receiver Sight (if mounted on receiver). See Sight Aperture.
Also Known As: Peep Sight, Receiver Sight
Related Terms: SIGHT APERTURE
ARM
1. To charge or load a firearm. 2. Contraction of “firearm.”
ARMOR PIERCING
1) A projectile designed to penetrate armor.
2) A regulatory term applied to projectiles based solely on their composition and construction details, regardless of actual ability to penetrate armor.
AUTOMATIC ACTION
A firearm design that continuously feeds cartridges, fires and ejects cartridge cases as long as the trigger is fully depressed and there are cartridges available in the feed system. Actuation of the mechanism may be from an internal power source such as gas pressure or recoil, or external power source, such as electricity.
Also Known As: Auto, Full Auto, Machine Gun
AUTOMATIC EJECTOR
A device in break-open firearms which expels fired cases when the action is opened.
AUTOMATIC FEED MECHANISM
A system for reloading a firearm utilizing some of the energy realized from firing a cartridge.
AUTOMATIC PISTOL
A common but improperly used term applied to autoloading pistols in use today. Most current “automatic” pistols are truly semiautomatic in action only. See Semiautomatic.
Also Known As: Automatic Fire
Related Terms: SEMIAUTOMATIC
AUTOMATIC RIFLE
A fully automatic shoulder firearm that starts firing when the trigger is pulled and continues until the trigger is released or ammunition is exhausted. The term should not be used in conjunction with semiautomatic firearms. See Semiautomatic.
Also Known As: Automatic Fire
Related Terms: SEMIAUTOMATIC
AUTOMATIC SAFETY
A safety device on some firearms intended to return to the On position when the action is opened.
AUXILIARY CHAMBER, AUXILIARY CARTRIDGE
An adapter that, when installed in a gun chamber for which it was designed, permits a smaller cartridge to be fired in the gun.
AVERAGE PRESSURE
The arithmetic mean of pressure measurements for a number of rounds in a single test.
BACK BORE
A shotgun, chambered for a specified gauge, whose barrel bore diameter is greater than the nominal specified for that gauge, but does not exceed SAAMI maximum.
BACK STRAP
The exposed metal strip at the rear of a pistol or revolver grip.
Also Known As: Strap
BACKSTOP
A structure intended to safely stop a fired bullet or other projectile(s).
BACKTHRUST
The force exerted on the breech block by the head of the cartridge case during propellant burn.
Also Known As: Bolt Thrust
BALL AMMUNITION
A term generally used by the military for a cartridge with a full metal jacket or solid metal projectile (bullet).
Also Known As: Ball Cartridge
BALL POWDER
Ball Powder is a registered trademark for propellant, owned by General Dynamics Ordnance and Tactical Systems, Inc. often misapplied to spherical propellants or flattened spherical propellants offered by other manufacturer.
BALL SCREW
A pointed, helical piece of metal secured at the end of a ramrod and used to remove a lead ball or patch from a muzzle loading gun.
BALLED SHOT
The fusing together of several pellets in a shotshell load, usually caused by hot propellant gases leaking past the wadding and fusing the shot while the shot is still in the barrel. See Fused Shot.
Related Terms: FUSED SHOT
BALLISTIC COEFFICIENT
An index of the manner in which a particular projectile decelerates in free flight expressed mathematically as: c = w/id2 where: c = ballistic coefficient, w = mass, in pounds, i = coefficient of form (a.k.a. form factor), d = bullet diameter, in inches. Represents the bullet’s ability to overcome the air resistance in flight.
BALLISTIC TABLE
A descriptive and performance data sheet on ammunition. Information usually includes: bullet weight and type; muzzle velocity and energy; velocity; energy and trajectory data at various ranges.
BALLISTICS
The science of projectiles in motion. Usually divided into three parts: 1.) Interior Ballistics, which studies the projectile’s movement inside the barrel of a firearm; 2.) Exterior Ballistics, which studies the projectile’s movement between the muzzle and the target; and 3.) Terminal Ballistics, which studies the projectile’s movement in the target.
BAR SIGHT
A rear sight that incorporates a high visibility, typically horizontal, bar immediately below the rear sight notch. Usually used in conjunction with a high visibility dot front sight.
BARREL
Firearm component through which a projectile travels. May be rifled or smooth bore.
BARREL ASSEMBLY
A barrel of a firearm, either fixed or interchangeable, that has been fitted with necessary parts so that it may be assembled to the remainder of the firearm.
BARREL BAND
A strip or strips of metal that encircle and hold the barrel and stock, fore-end, magazine or other accessories together.
BARREL BLANK
An unfinished barrel in any state of completion.
Also Known As: Blank
BARREL CHANNEL
A groove in a rifle stock or fore-end where the barrel fits in the assembled position.
BARREL DIAMETER
The outside dimension of a barrel at any given point.
BARREL EROSION
The wearing or physical deterioration of the bore or chamber of a firearm caused by hot propellant gases or projectile passage.
BARREL EXTENSION
A metal projection which extends rearward from the breech end of a barrel into which the breech locks while the firearm is in battery or firing position.
BARREL GUIDE
A ring shaped attachment on the barrel of many shotguns which encircles the magazine tube. Sometimes called Magazine Tube Bracket.
Also Known As: Magazine Tube Bracket
BARREL JACKET
A tube that surrounds the barrel.
BARREL LENGTH
On shoulder arms and most handguns the distance between the muzzle of the barrel and the face of the breech block or bolt. On revolvers, it is the overall length of the barrel only, including the portion within the frame.
BARREL LIFE
The total number of rounds fired in a barrel before it becomes unserviceable.
BARREL LUG
A general term for any projection extending at right angles to the barrel.
BARREL OBSTRUCTION
Also called bore obstruction. A foreign object or material in the bore of a barrel which prevents unhindered passage of projectile(s) when fired.
BARREL PRESSURE
The pressure in a barrel developed by propelling gases when a cartridge is fired.
BARREL REFLECTOR
Also called bore reflector. A device with a mirror for examining the bore and chamber of a barrel.
BARREL RELINING
The replacement of the interior surface of a bore by inserting and fastening a tube. Usually refers to rifled barrels.
Also Known As: Barrel Liner
BARREL SHANK
The breech end of the barrel that fits into the action or receiver.
BARREL SLEEVING
This term usually refers to shotgun barrels. See Barrel Relining.
Related Terms: BARREL RELINING
BARREL STEP
An abrupt change in external barrel contour.
BARREL STRIKING (DRAWFILING)
The longitudinal hand filing of a barrel on its exterior surface to produce a smooth finish.
BARREL THREADS
1. Threads found on the breech of the barrel, used to screw some barrels into the frame or receiver of the firearm. 2. Threads found on the muzzle end of the barrel, used to attach a muzzle device
BARREL TIME
The elapsed time from the contact of a firing pin with a cartridge primer to the emergence of the projectile(s) from the muzzle of the firearm.
Also Known As: Ignition Barrel Time
BARREL VENT
An opening or series of openings or ports in a barrel, normally near the muzzle, through which gases pass prior to bullet exit. See Muzzle-Brake.
Related Terms: MUZZLE BRAKE
BARREL VIBRATION
The oscillations of a barrel as a result of firing.
BARREL WEAR
The gradual mechanical deterioration caused by use, i.e. firing, cleaning, etc. Also, see Barrel Erosion.
Related Terms: BARREL EROSION
BARREL WEIGHT
A separate weight attached to a regular barrel to change balance.
BARREL WHIP
The movement of the muzzle end of a barrel that occurs as the projectile leaves.
BARREL-CYLINDER GAP
The opening or clearance between barrel and cylinder in a revolver. See also Cylinder Gap.
Related Terms: CYLINDER GAP
BARRELED ACTION
The combination of barrel and receiver or frame together with the other parts of the mechanism by which a firearm is loaded, fired and unloaded.
Also Known As: Barreled Receiver
BASE WAD
A cylindrical component that is assembled into the head end of a shotshell.
BATTERY
The condition where the breech of the action is in proper position for firing.
BATTERY CUP
A component of a shotshell primer; a flanged metallic cup that contains and supports the primer cup and anvil.
BATTERY CUP PRIMER
1. A flanged metal cup having a flash hole at the bottom end. 2. An ignition component using a battery cup as a holder for the other elements, usually found in shotshells.
BAYONET LUG
A feature on a firearm designed to allow the mounting of a bayonet.
BB
The designation of spherical shot having a diameter of .180” used in shotshell loads. The term BB is also used to designate steel or lead air rifle shot of .175” diameter. Although the two definitions cause some confusion, they have coexisted for many years.
BB CAP
The abbreviation for Bulleted Breech Cap. The original design in 1845 was a percussion cap without a well defined head loaded with a 22 caliber ball. A rimfire cartridge designed for use in Flobert rifles for indoor use. Several variations followed.
BEAD SIGHT
A spherical sight typically used on shotgun barrels.
BEARING SURFACE
That portion of a bullet’s outer surface that comes into direct contact with the interior surface of the barrel bore when moving through the barrel.
Also Known As: Band
BEAVERTAIL FORE-END
A wider than normal, usually flattened, forward part of a stock.
BEAVERTAIL FOREARM
A wider than normal, usually flattened, forward part of a two-piece stock.
BEDDING
Refers to the fit or fitting of the metal parts of the barrel and receiver with the wood stock.
BEDDING CONTROL
1. An adjustable device, which is installed in the fore-end of a rifle stock to provide pressure on a barrel. 2. The pressure provided by the wood-to-metal fit.
BEDDING SCREW(S)
A form of Bedding Control using machine screw(s) to produce a pressure on the underside of the barrel.
BELTED CARTRIDGE
A cartridge with a case design having an enlarged band ahead of the extractor groove. This design was originally intended to headspace cartridges with an insufficient shoulder angle (i.e. 300 H&H Magnum, 375 H&H Magnum).
Also Known As: Belted Magnum, Belted Case
BENCHREST
A table specifically designed to eliminate as much human error as possible by supporting a rifle for competitive shooting or for sighting-in purposes.
BENCHREST RIFLE
A rifle designed for optimum accuracy while being shot from the shoulder and supported by a specifically designed table (rest).
BENCHREST STOCK
Generally, a large and heavy stock used exclusively for benchrest shooting.
BENT
A notch, usually in the hammer, in which the sear or trigger is held under tension of the mainspring until released by movement of the trigger or hammer. See Half Cock. See Full Cock.
Related Terms: FULL-COCK, HALF COCK
BERDAN PRIMER
An ignition component consisting of a cup, explosive mixture and covering foil. The anvil is an integral part of the cartridge case head in the bottom center of the primer pocket. One or more flash holes are drilled or pierced through the bottom of the primer pocket into the propellant cavity of the base. Commonly found in European cartridges.
BIFURCATED LUMPS
A type of projection found mainly on top-break action gun designs. The bifurcated or divided projections are mounted on each side of the barrel (or lower barrel in over/under designs) and engage trunnions located on the receiver wall. This serves to reduce the overall height of the receiver-barrel assembly.
BIG BORE
A non-technical term generally referring any firearm using a centerfire rifle cartridge with a bullet .30” or larger in diameter.
BIG BORE CARTRIDGE
For target matches in the United States, cartridges utilizing bullets 0.300” in diameter or larger.
BILLIARD BALL EFFECT
The divergence of shot pellets caused by collisions of pellets in the shot string as it comes into contact with the target.
BIRD SHOT
A general term used to indicate any shot smaller than buckshot.
BIRD’S HEAD GRIP
A handgun grip that comes to a point in front, making it resemble a bird’s head.
BLACK POWDER
The earliest form of propellant, reputed to have been made by the Chinese or Hindus before the remote beginnings of history. First used for guns in the 13th century. It is a mechanical mixture of potassium or sodium nitrate (“saltpeter”), charcoal and sulfur.
BLADE SIGHT
Thin, flat projection used as the front sight on some firearms.
Also Known As: Front Sight Blade
BLANK CARTRIDGE
A cartridge loaded without a projectile designed to produce a loud noise. Often sealed at the mouth with a cardboard, plastic or fiber wad which is propelled from the muzzle with a dangerous force for a short distance when fired.
Also Known As: Blank
BLANK STOCK
A rough sawed piece of wood having the approximate external outline of a stock prior to final shaping.
Also Known As: Blank
BLANKED PRIMER
A fired primer cup in which the firing pin indent has been punched out by internal gas pressure.
BLIND BOX MAGAZINE
A magazine having a permanently closed bottom. Loading and unloading are accomplished through the same opening.
BLOW-BY
A leakage of propellant gas forward past the bullet in the barrel.
BLOW-FORWARD, BLOW-FORWARD ACTION
A self-loading action in which the breech block is stationary and the barrel moves forward to cycle the action.
BLOWBACK
A leakage of propellant gas rearward between the cartridge case and chamber wall.
BLOWBACK ACTION
A semiautomatic or automatic action whereby the rearward pressure of the propellant gases is transmitted through the interior of the cartridge case to the bolt or slide to initiate its rearward travel. The barrel and receiver are typically fixed in this type of action. As the bolt or slide moves to the rear it typically compresses a spring that, upon completion of the rearward travel, returns the bolt or slide into battery, and holds it in place. There are no other breech locking mechanisms in the firearm.
BLOWN PATTERN
A pellet distribution (pattern) with an unusually low percentage of pellets and/or of erratic distribution. Depending on its overall shape and pattern distribution, may also be referred to as a Doughnut Pattern.
BLOWN PRIMER
A primer that is separated completely from the cartridge or shotshell after firing due to severe expansion of the primer pocket and head.
BLUING
The chemical oxidation to color ferrous metal parts various shades of blue or black.
Also Known As: Blueing, Black Oxide
BLUING TANKS
Tanks used to contain the solutions used for bluing of firearms.
Also Known As: Bluing Tank
BOAT-TAIL BULLET
A specific design of bullet having a tapered or truncated conical base.
BODY (CASE)
1. The portion of the cartridge case which contains the propellant. 2. Shotshell – the tubular section that contains the propellant, wads and shot charge (if present).
BOLT ACTION
An action in which the bolt is in line with the bore at all times; manually reciprocated using a handle attached to the bolt to load, unload and cock. There are two principle types of bolt actions: the turn bolt and the straight pull type.
BOLT GUIDES
Grooves or ridges on either bolt or receiver intended to maintain alignment or prevent over-rotation.
BOLT HANDLE
A protrusion from the bolt, usually at right angles from the axis of the bolt, which is used to manually actuate the mechanism.
BOLT HANDLE BENDING JIG
A mechanism of two or more pieces which is used in the alteration of bolt handles.
BOLT HEAD
The forward end of the bolt containing the bolt face or breech face.
BOLT LOCKING LUG(S)
The protrusion or protrusions from the surface of the bolt body which lock into mating recesses in the receiver, barrel or barrel extension to resist rearward thrust of the chamber pressure.
Also Known As: Locking Lug, Bolt Lug
BOLT RACEWAY
Longitudinal grooves in the receiver in which the bolt lugs or other projections travel.
BOLT RELEASE
1. A device which allows the bolt to be removed from the firearm. 2. A device which allows the bolt to move into battery from the “hold open” position.
BOLT SLEEVE
A component at the rear end of the bolt which guides the firing pin and supports the firing-pin spring in bolt action rifles. Also called bolt plug.
Also Known As: Bolt Plug
BOLT STOP
A device which is intended to retain the bolt in the firearm during normal operation.
BOLT THROW
The distance the bolt travels from “fully open” to “fully closed” position.
BOOT
1. A protective device used on the buttstock of a firearm during test firing 2.A type of recoil pad.
BORE
The interior of a barrel forward of the chamber.
BORE AXIS
A theoretical line through the center of the bore.
Also Known As: Axis of Bore, Line of Bore
BORE BRUSH
A brush used to clean the interior surface of the barrel of a firearm.
BORE CASTING
The pouring of a special alloy or material that has a low melting point and exceptional dimensional stability into the bore or chamber of a firearm. The cast is used to study physical characteristics of the bore.
BORE CONSTRICTION
A reduction in the internal diameter of a firearm bore.
BORE DIAMETER
1. Rifled barrels: the minor interior diameter of a barrel which is the diameter of a circle formed by the tops of the lands. 2. Shotguns or muskets, the interior dimension of the barrel forward of the chamber but before any restrictive choke or expanded muzzle.
Also Known As: Land Diameter
BORE SIGHTING
A method of aligning a barrel on a target by aiming through the bore. May be part of the sight alignment procedure.
BORESCOPE
An illuminated, optical device for examining the interior of the bore of a firearm.
BOX LOCK ACTION
An action commonly used in break-open firearms in which the hammer and hammer springs are located within the frame and are self-cocking.
Also Known As: Boxlock Action
BOX MAGAZINE
A rectangular receptacle attached to or inserted into a firearm that holds cartridges stacked on top of one another ready for feeding into the chamber.
BOXER PRIMER
An ignition component consisting of a cup, explosive mixture, anvil and covering foil or disc which together form the completed primer ready for assembly into the primer pocket of a cartridge case. One central flash hole is pierced through the bottom of the primer pocket into the propellant cavity of the case. Used in modern commercial centerfire ammunition made in Canada and the United States.
BREECH
The end of the barrel where the ignition of the propellant takes place.
BREECH BOLT
The locking and cartridge head supporting mechanism of a firearm that operates in line with the axis of the bore.
Also Known As: Bolt
BREECH BORE SIGHT
A fixture having a small centrally located aperture that fits into a firearm chamber. Used in conjunction with a similar device that fits into the muzzle to establish the axis of the bore.
BREECH FACE
That part of the action which is against the head of the cartridge case or shotshell when in battery.
Also Known As: Bolt Face, Breech Block Face, Breech Bolt Face
BREECH PLUG
In percussion or flintlock firearms, the metal part that is threaded into the breech end of the barrel.
BREECH STANDING
That part of the frame of a revolver or break-open firearm which supports the head of the cartridge when it is fired.
BREECHBLOCK
A mechanism which does not operate in line with the axis of the bore, and which is intended to support, properly, the head of the cartridge.
BREECHING SPACE
A misnomer. Commonly confused with headspace.
BRENNEKE SLUG
A formed rifled slug with a wad assembly attached to its base by a screw for use in shotguns.
BRIDGE
A component of a firearm action which usually straddles other parts and acts as a guide or support.
BRIDGING POWDER
The wedging action of powder in the feed tube of a cartridge loading device causing stoppage of normal flow.
BRISANCE
A term describing the shattering power of high explosives.
BROACH RIFLING
The process of forming helical rifling grooves in the barrel of a firearm by a tool having a series of cutting edges each slightly larger than the preceding.
Also Known As: Barrel Broaching
BROWNING
A chemical oxidation process to color metallic parts of a firearm a brownish black shade.
BUCKHORN SIGHT
A rear sight for hunting rifles that has the V notch at the bottom of an almost completely closed “U.”
BUCKSHOT
Lead pellets ranging in size from .24” to .36” diameter normally loaded in shotshells.
BUFFER
1. In a firearm, any part intended to absorb shock, reduce impact or check recoil. 2. In a shotshell, any material added to the shot to prevent deformation during firing.
BULGE CHAMBER
A chamber with an abnormal enlargement.
BULGED BARREL
A localized enlargement of the barrel bore typically caused by the firing of a round into an obstruction within the barrel. If the bulge is circumferential: See Ring Bulge.
Related Terms: RING BULGE
BULL
A slang term for Bullseye of Target. See Bullseye.
Related Terms: BULLSEYE
BULL BARREL
A firearm built with an extra-thick, heavy barrel, used primarily for target shooting or varmint hunting.
Also Known As: Bull Gun
BULL PUP
A shoulder-fired firearm in which the action is behind the fire control system.
BULLET
A non-spherical projectile for use in a rifled barrel and sometimes contained within a sabot.
BULLET CASTING
A process for making lead bullets by pouring molten metal into a mold.
BULLET CORE
The inner section of a jacketed bullet, usually lead.
Also Known As: Core
BULLET CREEP
The movement of a bullet out of the cartridge case due to the recoil of the firearm (and the inertia of the bullet) when firing another cartridge in the firearm.
Also Known As: Bullet Jump, Bullet Popping
Related Terms: BULLET JUMP
BULLET DIAMETER
The maximum dimension across the largest cylindrical section of a bullet.
BULLET DROP
1. The difference between the bullet’s vertical position relative to the bore axis at any given point in its flight.
2. In ballistic performance tables, the deviation from the line-of-sight and the bullet’s position at any given point in its flight. In this usage, knowledge of the distance at which the sighting device is adjusted to yield a deviation of *zero* (“sighting-in” range) must be known.
Also Known As: Projectile Drop
BULLET ENGRAVING
1. The grooves cut into a bullet by barrel rifling. 2. The forming of grooves in a bullet by the barrel rifling.
BULLET JACKET
A separate layer in a bullet’s construction on at least the portion of the bullet engaging the firearm’s rifling.
BULLET JUMP
The distance that a bullet must travel from its position at rest in the cartridge case to its initial engagement of the rifling.
Also Known As: Free Travel
BULLET LUBRICATOR
The tool used to lubricate bullets.
BULLET MOLD
A split block of metal having one or more cavities into which molten lead is poured to form a bullet.
BULLET PENETRATION
That distance which a bullet travels into the target material.
BULLET PULL
The force required to extract a bullet from the case into which it was loaded.
BULLET PULLER
1. An instrument that measures the force required to extract a bullet from live ammunition. 2. A tool used to remove bullets from live ammunition.
BULLET SLIPPAGE OR STRIPPING
Slippage or stripping occurs if the bullet fails to engage the rifling properly.
BULLET SPIN OR ROTATION
The rotational motion imparted to the bullet by the rifling in the barrel.
BULLET SPINNER
A mechanical device used to detect the amount of eccentricity in a bullet between its rotational axis and the outer surface of the bullet.
BULLET SPLASH
The spatter and fragmentation of a bullet upon impacting a hard surface.
BULLET STABILIZATION
The principal to account for the steadiness of flight conferred upon an elongated projectile.
BULLET TIPPING
The instability of a bullet in flight in which the point of the bullet is not aligned with the direction of flight.
Also Known As: Tipping
BULLET TRAP
A device to safely stop a bullet in flight. Usually found in indoor ranges behind the target area.
BULLET UPSET
1. In Interior Ballistics: The change of bullet form due to chamber pressure. 2. In Exterior Ballistics: The expansion of a bullet upon impact with target.
BULLET WOBBLE
A characteristic caused by the eccentricity or imbalance of the bullet to the axis of the bore. See Yaw.
Related Terms: YAW
BULLET-PUSH
The force required to shorten a cartridge by pushing on the bullet.
BULLSEYE
In target shooting, the aiming point.
BUTT
1. Handguns: Bottom part of the grip. 2. Long Guns: Rear or shoulder end of the stock.
BUTT PLATE
A metal, rubber or composition covering to reinforce and protect the shoulder end of a firearm stock.
BUTT STOCK
The rear or butt end of the firearm which is normally placed against the shooter’s shoulder.
BUTTERKNIFE BOLT HANDLE
A flat, low profile, paddle-shaped bolt handle found on some rifles.
BUTTON RIFLING
A process wherein a hardened steel disc or button with a rifling cross section configuration is pushed or pulled through a drilled and reamed barrel so as to cold form the rifling grooves to the desired depth and twist.
CALIBER
1. A term used to designate the specific cartridge(s) for which a firearm is chambered. 2. Firearms: The approximate diameter of the circle formed by the tops of the lands of a rifled barrel, often expressed in hundredths of an inch (“.38 Caliber”) or millimeters (“7mm Caliber). 3. Ammunition: A numerical term included in a cartridge name to indicate a rough approximation of the bullet diameter.
CAM LOCK
A type of lock found in certain breechloaders, such as the 1873 Springfield. See Trap Door Action.
Related Terms: TRAP DOOR ACTION
CANNELURE
1. A circumferential groove generally of corrugated appearance cut or impressed into a bullet or cartridge case.
Also Known As: Grooves, Lube Groove
CANTING
The tipping or tilting of a gun to one side at the time it is fired.
CAP
1. An obsolete term referring to a primer. 2. Percussion Muzzle Loading: See Percussion Cap.
Related Terms: PERCUSSION CAP
CAP AND BALL
A muzzleloading firearm using the percussion cap ignition system.
CAP FLASH
The ignition of a primer or percussion cap produces a high temperature flash of hot gases, which is called the Cap Flash. Also called Primer Flash.
Also Known As: Primer Flash
CAPPED BULLET
Consists of a standard lead type bullet having a harder metal jacket (gilding metal, copper, etc.) over the nose.
CAPPER
A device that contains a quantity of percussion caps and simplifies the placement of the cap upon the nipple on a muzzle-loading firearm.
CARBINE
A rifle of relatively short length and light weight originally designed for mounted troops.
CARD WAD
A thin card-like disc placed over a shot load or powder. See Overpowder Wad.
Related Terms: OVERPOWDER WAD
CARRIER
A lifting mechanism in some repeating firearms that raises and positions the cartridge for feeding into the chamber. Sometimes called the Lifter.
Also Known As: Lifter
CARRIER DOG
A repeating action firearm component which engages or is attached to the carrier or lifter and acts to control its motion. Sometimes called Lifter Pawl.
Also Known As: Lifter Pawl
CARRYING STRAP
A simplified version of a sling, used for carrying purposes only.
Also Known As: Strap
CARTRIDGE
A single round of ammunition consisting of the case, primer and propellant with or without one or more projectiles. Also applies to a shotshell.
CARTRIDGE BLOCK
A flat container having blind holes into which cartridges can be inserted in an upright position to be readily available to the shooter.
CARTRIDGE BRASS
A copper alloy with a nominal composition of 70 percent copper and 30 percent zinc. “Cartridge Brass” is the trade name for the Copper Development Association, Inc. Alloy C26000.
CARTRIDGE CASE
The main body of a single round into which other components are inserted to form a cartridge. Usually refers to centerfire and rimfire cartridges. Serves as a gas seal during firing of the cartridge. Usually made of brass, steel, copper, aluminum or plastic. Also referred to as a shellcase.
Also Known As: Shellcase
CARTRIDGE CASE LENGTH
The dimensions from face of the head to the mouth.
Also Known As: Case Length
CARTRIDGE CLIP
A separate cartridge container to hold cartridges or shells in proper sequence for feeding into a specific firearm. It is a magazine charger, and unlike a magazine does not contain a feeding spring. Sometimes improperly called a Magazine.
CARTRIDGE COOK-OFF
The firing of a cartridge by extreme overheating in a firearm chamber, without operation of the firing mechanism. Usually associated with machine guns.
Also Known As: Cook-Off
CARTRIDGE GUIDE
A firearm component which acts as a guide for the cartridge while it is being fed from the magazine to the chamber.
CARTRIDGE RAMP
Surface in the receiver or barrel of a repeating action firearm along which the cartridge rides in feeding from magazine to chamber.
Also Known As: Feed Ramp
CARTRIDGE STOP
1. A mechanical device in firearms that allows only one shell to feed from the magazine with each cycle of the action. 2. A manually-operated device to prevent the feeding of cartridges from a magazine.
Also Known As: Shell Stop, Cartridge Cutoff, Shell Latch
CARTRIDGE, SMALL ARMS
A term used by the US Department of Transportation as defined by US Code of Federal Regulations (49 CFR 173.59): https://www.ecfr.gov/cgi-bin/text-idx?SID=bd5856259cccd9bf739fb6f683c1d2af&mc=true&node=se49.2.173_159&rgn=div8
CASE
Refers to cartridge case or shotshell case. Shortened through common usage to simply “case.”
CASE CAPACITY
Total available internal volume of a case when a primer is seated in the primer pocket.
CASE EXTRACTOR GROOVE
An annular groove cut in rimless, semi-rimmed cartridge or belted cases, forward of the head, for the purpose of providing a surface that the gun extractor may grip to remove the case from the chamber.
CASE FIRE-FORMING
A procedure used by handloaders to change the external shape of a cartridge case somewhat by firing in a gun having a chamber of the desired configuration. The case to be fireformed must be dimensionally similar to the desired configuration, especially in the case head area.
Also Known As: Fire-Form
CASE GAUGE
A fixture used to inspect cartridge case dimensions (i.e. length, diameters, thickness, etc.) to insure conformance to established tolerances.
CASE HEAD EXPANSION
An enlargement of the cartridge case head diameter on firing.
CASE LIFE
An expression of the number of times a case can be reloaded and fired.
CASE MOUTH
The opening in the case into which the projectile or shot is inserted.
CASE MOUTH CHAMFERING
A manual operation performed on cartridge cases prior to reloading to ease insertion of projectiles or chambering. Can be internal and/or external.
CASE SHOULDER
The angled or tapered section of a bottleneck cartridge case connecting the main body of the case to the smaller diameter neck.
CASE SPLIT
A longitudinal rupture in the wall of a cartridge case or shotshell.
Also Known As: Split Case
CASE STRETCHING
The elongation in the body of a cartridge case during firing.
CASE TAPER
The gradual reduction in diameter of a cartridge case from head to shoulder or mouth.
CASE TRIMMER
A devise used to remove material from the case mouth in order to shorten the case to within the max and min specification for that particular case.
CASELESS AMMUNITION
Ammunition that has the propellant charge attached to the bullet and not enclosed in any type of cartridge case.
CAST BULLET
A bullet formed by pouring molten lead alloy into a mold.
CAST-NEUTRAL
The buttstock of a firearm which has neither cast-on or cast-off relative to the centerline of the barrel.
CAST-OFF
The offset of the butt of a shoulder-fired firearm to the right for a right-handed shooter and to the left for a left-handed shooter. See Stock Dimensions.
Also Known As: Cast
CAST-ON
The offset of the butt of a shoulder-fired firearm to the left for a right-handed shooter and to the right for a left-handed shooter. See Stock Dimensions.
Also Known As: Cast
CASTING
The act of forming an object, such as a bullet, by pouring molten material into a mold.
CB CAP
A low velocity caliber 22 rimfire cartridge having a conical bullet (“CB”) loaded in a case shorter than the 22 short.
CENTER OF IMPACT
The center of a shot pattern or bullet impacts on a target made by a series of rounds fired at the same aiming point.
CENTERFIRE CARTRIDGE
Any cartridge intended for use in rifles, pistols and revolvers that has its primer central to the axis in the head of the case.
CENTERFIRE PRIMER
A cartridge initiator which is assembled central to the axis of the head of the cartridge case and which is actuated by a blow to the center of its axis, as opposed to a rimfire primer, which must be struck on the circumference of the cartridge head.
CHAMBER
1. In a rifle, shotgun or pistol, the rearmost part of the barrel that has been formed to accept a specific cartridge or shell when inserted 2. In a revolver, the holes in the cylinder that have been formed to accept a cartridge.
CHAMBER CAST
A low melting point material or alloy casting made of a chamber to determine internal chamber dimensions.
CHAMBER LEADE
The conical transitional zone of the chamber between the forward end of the casemouth, or free-bore if present, and the end of the taper into the rifling.
Also Known As: Throat, Ball Seat
Related Terms: THROAT, BALL SEAT
CHAMBER PRESSURE
That pressure created in the chamber of a firearm by the expanding propellant combustion gases. Normally measured by means of a piezoelectric pressure transducer or a copper crusher.
Also Known As: Breech Pressure
CHAMBER REAMER
One of a series of cutting tools used to form the chamber area of a barrel bore.
CHARGE
1. The amount, by weight, of a component of a cartridge (i.e., priming weight, propellant weight, shot weight.) 2. To load a firearm.
CHECKERING
A diamond-like pattern in the wood, plastic or metal components of a firearm for improving grip or ornamentation.
CHECKERING CRADLE
A frame having vertical end supports between which a gun stock may be held while its gripping surfaces are being checkered.
CHECKERING LINE COUNT
A method of expressing the size of the diamonds in a checkering pattern, expressed in lines per inch The higher the number, the finer the pattern; the lower the number, the coarser.
CHECKERING TOOLS
The tools used for cutting a checkering pattern in wooden stocks. May be hand or machine powered.
CHEEKPIECE
A raised part of the side of the stock of a shoulder-arm against which the shooter rests his face.
Also Known As: Cheek
CHERRY
A tool used to cut the precise bullet configuration into the two halves of a bullet mold.
CHILLED SHOT
Lead Shot containing more than 0.5% alloying metal to increase its hardness. Also called Hard Shot.
Also Known As: Hard Shot
CHOKE
An interior constriction at or near the muzzle end of a shotgun barrel for the purpose of controlling shot dispersion.
CHOKE MARKINGS
While no choke marking standard exists, typical choke markings are (in order from greatest to least constriction):
Full Choke = F, Full, * or I
Improved-Modified = IM, Imp. Mod., ** or II
Modified = M, Mod, *** or III
Improved Cylinder = IC, Imp. Cyl., **** or IIII
Skeet = SK, Skeet
Skeet USA = SK USA
Cylinder = CL, Cyl.
Some firearm manufacturers in the Europe also use the United States system.
CHOKE TUBE
A replaceable insert in the muzzle of a shotgun barrel to provide the desired amount of choke.
CHOPPER LUMP
A type of lump which is integral with the barrel. See Lump.
Related Terms: LUMP
CHRONOGRAPH
An instrument designed to measure elapsed time. When correlated with distance it is used to determine projectile velocity.
CLAY TARGET
A circular, domed, frangible disc used as an aerial target for shotgun shooting games. Originally formed out of clay, modern “clay” targets are generally made from a formulation of pitch and limestone. Dimensions and weights are regulated by skeet and trap shooter’s associations. Also called Clay Bird or Clay Pigeon.
Also Known As: Clay Bird, Clay Pigeon
COATED BULLET
Lead bullet, having a thin coating of another material such as brass, copper, nylon, etc.
COCK
To place the hammer, firing pin or striker in position for firing.
COCKING INDICATOR
Any device to indicate that a firearm hammer or striker is cocked.
COCKING LEVER
A mechanical means of cocking the hammer or striker of some firearms using a manually operated, external lever.
COCKING ON CLOSING
In relation to bolt action firearms, when the striker is cocked by closing the bolt.
COCKING ON OPENING
In relation to bolt action firearms, when the striker is cocked by lifting the bolt handle.
COCKING PIECE
1. In certain firearms, the end of a long firing pin or striker by which the firearm may be manually cocked. 2. An internal portion of the cocking mechanism, which holds the firing pin or striker in it’s cocked position against the sear.
COCKING ROD
A mechanical means of cocking the hammer of some firearms.
COCKING STUD
Small lug in the cocking mechanism of a firearm.
COEFFICIENT OF FORM
A numerical term indicating the general profile of a projectile.
Also Known As: Form Factor
COMB
In a shoulder arm, the ridge at the upper forward part of the butt stock just in back of the grip section.
COMBINATION GUN
A multiple barrel firearm designed to fire different calibers or types of ammunition.
COMBUSTION
The chemical reaction of a fuel and oxygen, usually initiated by a heat source. In the context of interior ballistics, the result of this reaction is gas and heat generation, increasing pressure in an enclosed space.
COMMERCIAL BRONZE
A copper alloy with a nominal composition of 90 percent copper and 10 percent zinc. “Commercial Bronze” is the trade name for the Copper Development Association, Inc. Alloy C22000. It is used in the manufacture of bullet jackets. See also “Gilding Metal.”
COMPENSATOR
A muzzle attachment or feature to redirect propellant gases with a goal of reducing muzzle lift.
CONFORMAL GAUGE
A design of piezoelectric transducer system in which the sensing end matches the internal curvature of the chamber.
CONFORMAL TRANSDUCER
A design of piezoelectric transducer system in which the sensing end matches the internal curvature and taper of the chamber.
Also Known As: Transducer, Piezoelectric Pressure
COPPER CLAD STEEL
A laminated structure of copper and steel used for the manufacture of certain bullet jackets.
COPPER JACKETED BULLET
A bullet having an outer jacket of copper or copper alloy, and containing a lead alloy core.
CORROSIVE PRIMER
A priming mixture that contained compounds of chlorine and oxygen generally used in military ammunition made before 1952. The residues are hygroscopic and, therefore, promote rusting.
CRACKED RIM
A radial rupture of the head and rim of a rimfire cartridge or shotshell.
CRANE
The part of a solid frame revolver on which the cylinder is swung out to accomplish loading and ejecting.
Also Known As: Yoke
CRISP TRIGGER
A trigger that releases without sensible movement.
CROSS BOLT SAFETY
A type of manual firearm safety operated by a lateral force on a button usually located in the trigger guard. Also called Push-Button Safety.
Also Known As: Push Button Safety
CROSSBOLT
1. A transverse operating type of lock used in some break-open type firearms (sometimes called a “Greener Crossbolt”). 2. A device intended to prevent stock splitting due to recoil. 3. A form of manual safety which operates transversely to prevent or permit firing of a gun.
CROTCH FIGURE
The generally irregular grain pattern common to a stock blank cut from the crotch of a tree.
CROWN
A feature on the muzzle of the barrel that is concentric and perpendicular to the bore axis. The purpose is to promote accuracy and protect the rifling at the muzzle.
Also Known As: Muzzle Crown
CROWNING
The act of applying a crown.
Related Terms: CROWN
CRUSHER
A calibrated metallic cylinder that, when used in conjunction with specific associated equipment, measures chamber pressure or firing pin indent.
CUP (COPPER UNIT OF PRESSURE)
A pressure value determined by means of copper crusher cylinders using SAAMI recommended procedures and equipment.
CUP SPLIT
A longitudinal split in the sidewall of the brass or steel cup assembled on a plastic or paper shotshell.
CUP WAD
A powder and shot separator of a shallow cup design which when loaded with lips down acts to help seal powder gases and so protect the rear of the shot column.
CUT CHECKERING
Checkering which is cut with a tool into the surface, either by hand or machine, rather than impressed.
CUT CHOKE
A choke formed by a reamer during manufacture of the barrel of a shotgun.
CUT OFF RUPTURE
A generally circumferential separation in the side wall of a cartridge case. May be complete or partial.
CUT RIFLING
A process of forming the helical grooves in the bore of a rifle barrel by a cutting tool which has a hook shape. Also called Hook Rifling.
Also Known As: Hook Rifling
CYCLIC RATE
The rate which a succession of movements repeats itself; in an automatic firearm, it is usually expressed in shots per minute that are theoretically possible to be fired, given an unlimited supply of ammunition.
CYCLING AN ACTION
The act of chambering a cartridge, firing the cartridge, opening the action, ejecting the spent cartridge case, and loading the next cartridge if applicable.
Also Known As: Firing Cycle
CYLINDER
The rotating part of a revolver that contains the cartridge chambers.
CYLINDER ALIGNMENT
The relationship of the axis of the chamber in a revolver cylinder to the axis of the bore.
Also Known As: Cylinder Timing
CYLINDER BORE
A shotgun barrel with a uniform interior diameter forward of the forcing cone to the muzzle end of the barrel.
Also Known As: Cylinder Bore Choke
CYLINDER END-PLAY
The free longitudinal movement of the cylinder in the frame.
Also Known As: Cylinder End Shake, Cylinder End-Play
CYLINDER GAP
In a revolver, the space between the cylinder and the barrel measured with the cylinder in the rearmost position.
Also Known As: Cylinder Gap, Barrel-Cylinder Gap, Cylinder-Barrel Gap
CYLINDER INDEXING
In revolver-type firearms, the rotational movement of the cylinder to bring the next chamber into alignment with the bore.
CYLINDER PIN
The pin around which the cylinder of a revolver rotates. This is a feature found on revolvers in which there is no crane. Also called Axis Pin, Base Pin, Center Pin.
Also Known As: Axis Pin, Base Pin, Center Pin
CYLINDER RELEASE LATCH
A device which permits the swinging out of the cylinder from the frame of a revolver.
Also Known As: Thumb Piece
CYLINDER STOP
A device to stop cylinder rotation in proper alignment with the barrel in a revolver. Sometimes called a Cylinder Latch or Cylinder Bolt.
Also Known As: Cylinder Latch, Cylinder Bolt, Bolt
CYLINDER STOP NOTCH
One of the machined grooves on the circumference of a revolver cylinder that is engaged by the cylinder stop in order to assure barrel and chamber alignment. Also called Bolt Notch.
Also Known As: Bolt Notch
DAMASCUS BARREL
A barrel formed by twisting or braiding together steel and iron wires or bars. The resulting cable is then wound around a mandrel and forged into a barrel tube. Sometimes called a Laminated Barrel.
Also Known As: Laminated Barrel
DATUM
A reference plane, point or diameter that provides a base for calculations and measurements.
DEAD BLOW ACTION
A blow back action that utilizes a sliding weight, usually made of a dense material such as tungsten, in conjunction with the breechblock to counteract the effect of the breechblock inertia and retard the cyclic rebound rate of the breech block.
DECAPPER
A tool used to remove primers from cartridge cases or shells.
DEFINITIVE PROOF CARTRIDGE
A cartridge loaded to specific pressures higher than service loads. Used only for testing assembled firearms or elements of firearms which contain the primary firing pressure.
Also Known As: Proof Load
DEFLAGRATION
A rapid combustion reaction which is propagated at a sub-sonic rate by heat transfer into the reacting material. This reaction is accompanied by a vigorous evolution of heat and flame. The flow of reaction products is in the direction opposite that of the combustion propagation (unlike DETONATION). Deflagration is usually dependent upon having fuel and oxidizing agent in very close contact, either from having the fuel as a finely divided mixture with the oxidant, or by combining the two in the same chemical compound or mixture. Deflagration exhibits a dependence upon the surrounding gas pressure.
DEFLECTION
The variation in the normal flight path of a projectile caused by external influences.
DEFLECTOR
A device mounted on the receiver or frame of a firearm to change the direction of an ejected case.
DELAYED BLOWBACK ACTION
An action in which a mechanical means in conjunction with bolt mass is utilized to gain additional delay prior to bolt opening. Also called Retarded Blowback.
Also Known As: Retarded Blowback
DELAYED FIRE
Any delay in firing of an abnormal duration. This implies that firing does eventually occur.
Also Known As: Hangfire
DEMI-BLOCK
A type of double barrel construction in which the two barrels are fastened together.
DENT REMOVER
A gunsmithing tool used to remove dents from shotgun barrels. Also called Dent Raiser.
Also Known As: Dent Raiser
DERRINGER
A generic term applied to many variations of small one-or two-shot pistols, using both percussion caps and cartridges. The original designer, Henry Deringer, spelled his name Deringer, not Derringer.
DESIGNATION – METRIC CARTRIDGE
Most foreign and some American commercial cartridges are identified by their nominal bullet diameter and cartridge case length, both of which are given in millimeters-e.g., 8×57, 7×57, 6.5x54mm.
DETENT
Indentation used as a stop for a spring-load lock.
DETONATION
An extremely rapid exothermic decomposition reaction which proceeds at a rate greater than the speed of sound within the reacting material (unlike DEFLAGRATION). The normal mode of initiation is shock (such as a blasting cap or high level mechanical shock), or from initial combustion which, due to peculiarities of confinement or other circumstances accelerates to such a degree that a shock wave is formed. Behind the shock wave is a reaction zone where material is converted to gaseous products at high temperature and pressure. The flow of the reaction is in the same direction as the propagation.
DEWAT
An abbreviation for DEactivated WAr Trophy.
DISCHARGE
To cause a firearm to fire.
DISCONNECTOR
A device intended to disengage the sear from the trigger. 1.) In a manually operated firearm, it is intended to prevent firing without pulling the trigger. 2.) In a semiautomatic firearm, it is intended to prevent full automatic firing. 3. A device that prevents out-of-battery firing.
DISINTEGRATING BULLET
Bullet that breaks into small pieces in flight or upon impact with the target.
Also Known As: Frangible
DISINTEGRATING PROJECTILE
A projectile that breaks up after leaving the muzzle and before it hits the target.
DISJUNCTOR
An electronic pulse forming device used in measuring projectile velocities.
DISPERSION
The greatest distance between any two bullet holes on a target, normally measured center-to-center.
DOLL’S HEAD
A usually round extension at the top of the barrel or rib of a shotgun which fits into a matching hole in the top of the standing breech.
DOMINANT EYE, MASTER EYE
The eye that controls both eyes when pointing toward or picking out an object.
DOUBLE ACTION
A firing mechanism in which the trigger serves the dual purpose of cocking and then releasing the firing mechanism – either hammer or striker. Double action firearms can be manually cocked similar to single action mode. For differentiation, see Single Action and Double Action Only.
DOUBLE ACTION ONLY
A firing mechanism in which the trigger serves the dual purpose of cocking and then releasing the firing mechanism – either hammer or striker. Double action only (DAO) firearms cannot be manually cocked to emulate single action mode. For differentiation, see Single Action and Double Action.
DOUBLE ACTION PISTOL
A pistol mechanism in which a single pull of the trigger cocks and releases the hammer.
DOUBLE ACTION REVOLVER
A type of revolver in which the rotation of the cylinder, cocking and firing are performed by a single pull of the trigger. Most Double Action revolvers can also be fired in the single action mode by manually cocking the hammer.
DOUBLE BARREL SHOTGUN
A shotgun with two barrels adjacent to each other in the horizontal plane (See Side-by Side). If arranged vertically, it is usually termed an “over/under” shotgun.
DOUBLE BASE POWDER
A propellant composed of colloided nitrocellulose and nitroglycerin as its base as opposed to single base powder which has colloided nitrocellulose only as its base material. The percentage of nitroglycerin added ranges from a low of 3% to a high of 39%.
DOUBLE PULL TRIGGER (2 STAGE)
A trigger which has two distinctive pull characteristics. The first or take-up stage is usually long and light in pull force; the second stage having a short but distinct increase in the pull force required to discharge the firearm.
DOUBLE SET TRIGGER
An arrangement of two triggers in which the actuation of one trigger presets the second resulting in a light trigger pull of the latter.
DOUBLE TRIGGER
A term used for firearms having two barrels and a separate trigger for the discharge of each. This term does not apply to firearms with double set triggers.
DOUBLE-BARREL
Two barrels in a firearm mounted to one frame. Can be vertically (“over-under”)or horizontally (“side-by-side”) aligned.
DOUBLE-GUN
A two-barrel firearm, usually side by side. Also known as Double Barrel or Double.
Also Known As: Double-Barrel, Double
DOUBLING
Simultaneous discharge of both barrels of a double-gun with a single pull of the trigger.
DOUGHNUT PATTERN
A pattern whose central area has few or no pellet hits.
DRAM EQUIVALENT
See “What does “dram equivalent” mean on shotgun ammunition
DRAW MARK
1. Ammunition – a longitudinal scratch on a cartridge case caused by foreign material on either the draw punch or die during fabrication. 2. Arms: See Witness Mark.
Related Terms: WITNESS MARK
DRILLING
A three-barreled long gun in which a combination of smoothbore and rifled barrels is used.
DROP SAFETY
A passive safety mechanism that prevents unintentional firing when the firearm is dropped.
DROP SHOT
Lead shot containing less than 0.5% alloying metal. Also called Soft Shot.
Also Known As: Soft Shot
DROPPED PRIMER
One that is separated completely from the cartridge or shotshell after firing without obvious distortion of the primer pocket and head.
DRY FIRE
The practice of “firing” a firearm without the use of live ammunition.
Also Known As: Dry Firing
DUMDUM BULLET
An obsolete term referring to an expanding bullet manufactured at the British Arsenal in Dumdum, India around 1900.
DUMMY CARTRIDGE
An inert cartridge which cannot be fired under any circumstances. In America, an inert cartridge for gun functioning is usually black oxidized and may or may not have holes in the side wall of the case. An inert cartridge for display may be natural colored and should have a hole in the primer cup with holes in the side wall of the case optional.
DUPLEX LOAD
1. A cartridge case containing two projectiles with a single powder charge. 2. A cartridge case containing a single projectile with two types of powder.
DUST COVER
1). A cover over the ejection port of a firearm to reduce the possibility of the entrance of foreign matter into the action. 2). The forward part of a pistol frame which protects the recoil spring.
DUST SHOT
Lead shot having a nominal diameter of .040” or smaller.
EAR PROTECTION
A recommended safety practice utilizing approved earplugs or muffs.
Also Known As: Hearing Protection
EFFECTIVE RANGE
The maximum distance at which a projectile can be expected to be useful.
EJECTION
The act of expelling a cartridge or fired case from a firearm.
EJECTION PORT
An opening in a receiver or slide for the ejection of spent or live rounds. This feature may also be used for loading of ammunition. See Loading Port
Related Terms: LOADING PORT
EJECTOR
A device which expels cartridges or fired cases from a firearm.
EJECTOR ROD
That component which actuates the extractor and/or ejector. Can be manual or automatic. Also called Extractor Rod.
Also Known As: Extractor Rod
ELECTRICAL TRAP
An electro-mechanical device for throwing clay targets.
ELEVATION ADJUSTMENT
The vertical movement of a sight to compensate for vertical displacement of a bullet or bullets from the aiming point.
ENGINE TURNING
A geometric design of abrasively formed overlapping circles on the metallic surfaces of a firearm.
Also Known As: Jeweling
ESCUTCHEON
A metal or plastic reinforcement around a screw hole.
EXPANDER PLUG
1. A plug of proper diameter that is inserted into the neck of a resized cartridge case to expand the diameter to allow the case to accept a bullet. 2. A tool used to remove dents in shotgun barrels.
Also Known As: Ball Sizing Plug
EXPANDING BULLET
A hunting bullet design that provides for controlled expansion upon impact.
EXPLODING BULLET
A bullet containing an explosive in the nose, intended to explode on impact.
EXPLOSION
The sudden release of energy of sufficient magnitude to create a pressure wave. The energy to produce an explosion may come from a variety of sources; including nuclear, pressure or chemical reaction. 1. Examples of pressure related explosions include a rapid change in state (liquid to gas, for example) or by the over pressurization of a container (i.e., the failure of a gas cylinder). 2. A chemical explosion is the event in which a quantity of matter is instantaneously converted to gaseous product, with the generation of high temperature and pressure.
EXPRESS SIGHT
A rear sight that incorporates a shallow “V” sight notch. They are used for fast target acquisition and are typically found on rifles intended for use on dangerous game.
EXTERIOR BALLISTICS
The branch of Applied Mechanics related to the motion of a projectile from the muzzle of a firearm to the target.
EXTRACTION
The act of withdrawing a cartridge or fired case from the chamber of a firearm.
EXTRACTOR
Device for withdrawing the cartridge or fired case from the chamber.
EXTRACTOR CUT
Usually a recess in the barrel of a firearm to accommodate an extractor.
EXTRACTOR GROOVE
A groove turned in the side wall of a cartridge case just forward of the rim for the purpose of extraction.
EXTREME HORIZONTAL SPREAD
The horizontal distance between the farthest right and left shots.
EXTREME SPREAD
The distance between the centers of the two shots which are the farthest apart of a group of shots on a target.
EXTREME VERTICAL SPREAD
The vertical distance between the upper-most and lower-most shots.
EYE PROTECTION
A recommended safety practice utilizing approved safety glasses.
FAIL-TO-FIRE
A failure of the firearm to discharge after the trigger has been pulled. It can be one of two types: 1.) a complete misfire, or 2.) a delayed fire.
FALLING BLOCK ACTION
An action in which the breech block moves vertically, or nearly so, inside of the receiver walls. Also called a dropping block.
Also Known As: Dropping Block Action, Drop Block Action, Ballard Action
FEED THROAT
A component which guides a cartridge from the magazine to the chamber.
FIELD LOAD
A shotshell loaded for hunting small game animals and birds.
FILLER WAD
Discs of various shapes and thicknesses used to adjust the volume of the contents of a shotshell.
FIRE CONTROL
The mechanism that utilizes trigger action to release the energy to initiate the primer. It may include but not lmited to the trigger, hammer, sear, disconnector, and/or safety.
Also Known As: Fire Control System
FIREARM
1). An assembly of a barrel and action from which a projectile is propelled through a deflagration of propellant. 2). The serialized portion of a frame or receiver.
FIRING PIN
That part of the firearm mechanism which strikes the primer or the rim of a cartridge to initiate ignition in order to fire the cartridge.
FIRING PIN INDENT
1. The impression made by the firing pin in the primer cup of the centerfire primer or the rim of rimfire cartridges. 2. A measure of the kinetic energy delivered by the firing pin.
FIRING PIN PROTRUSION
The distance the firing pin protrudes from the breech face when it is in its most forward position.
FIVE-IN-ONE BLANK
A blank cartridge that was designed for use in firearms of different calibers. It can be used in caliber 38-40, 44-40, and 45 Colt revolvers and in caliber 38-40 and 44-40 rifles.
FLAKE POWDER
A type of smokeless propellant in the form of thin discs or cut squares.
FLASH HIDER
A muzzle attachment designed to reduce muzzle flash. Also called Flash Suppressor.
Also Known As: Flash Suppressor
FLASH HOLE
1. A hole pierced or drilled through the web in the primer pocket in a centerfire cartridge case. 2. The hole in the end of a battery cup primer used in shotshells.
FLASH SUPPRESSANT
A material that is added to propellant for the purpose of reducing muzzle flash.
FLAT NOSE PROJECTILE
A projectile which is flat at its forward end.
FLAT TRAJECTORY
A relative term for minimal arching in the flight of a projectile. Generally, the faster the speed of the projectile, the flatter it’s trajectory.
FLAT-NOSED BULLET
A bullet with flattened front end perpendicular to the axis.
FLATTENED PRIMER
1. A condition where the normally rounded corners of a fired primer cup are squared due to internal pressures. 2. A primer cup configuration in which the crown is flattened to alter sensitivity.
FLINT LOCK
A muzzleloading firearm ignition system wherein a piece of flint is secured to the hammer in such a manner as to strike steel upon hammer release, causing sparks which ignite powder contained in the ignition system, for subsequent ignition of the main powder charge.
FLOATING CHAMBER
A system in which a rearwardly movable chamber operates the mechanism of a firearm when fired.
FLOATING FIRING PIN
A design in which the forward motion of the firing pin is unrestrained by a spring or other mechanical means.
Also Known As: Free Floating Firing Pin
FLOOR PLATE
The bottom of a box magazine. May be hinged, sliding or immovable.
FLUTED BARREL
A barrel with longitudinal grooves cut into the outside surface for all or some portion of the overall length.
FLUTED CHAMBER
A chamber that has longitudinal grooves.
FLUTING
1. See Oil-Dent. 2. Longitudinal grooves in the sidewall of a firearm chamber. 3. See Fluted Barrel.
Related Terms: FLUTED BARREL, OIL DENT
FLYER
1. A shot considerably outside the normal group on a target. 2. A shot considerably outside the normal range with regards to velocity or pressure.
Also Known As: Stray
FOIL
Part of a primer. See Paper Disc.
Related Terms: PAPER DISC
FOLDING SIGHT
A front or rear sight that can be folded down.
Also Known As: Leaf Sight
FOLLOWER
That part in a firearm which, through the action of a spring, forces a cartridge or cartridges to move.
FORCING CONE
1. The tapered leade from the shotgun chamber diameter to the bore diameter. 2. The tapered leade from the bore diameter to the choke diameter. 3. The tapered entrance to the bore in the rear of a revolver barrel.
FORE-END
Traditionally, the forward portion of a one-piece stock. Sometimes called a Forearm.
Also Known As: Forearm
FORE-END LUG
A protrusion found on the bottom of the barrel(s) (or lower barrel in over/under firearms) that serves as the attachment point of the fore-end. Typically associated with top-break action firearms.
FOREARM
Traditionally, the forward part of a two-piece stock. Sometimes called a Fore-end.
Also Known As: Fore-End
FRANGIBLE BULLET
A projectile designed to readily break up upon impact on a hard surface in order to minimize ricochet or spatter.
Also Known As: Gallery Bullet
FRANGIBLE PROJECTILE
Originally designed for law enforcement training, frangible ammunition’s projectile is designed to break up upon impact with hardened (e.g. AR500) steel into fragments small enough to prevent injury from ricochet/splash-back at typical practice distances. Ammunition loaded with frangible projectiles is sometimes referred to as “Reduced Hazard.”
FREE BORE
A portion of the chamber, usually cylindrical, forward of the casemouth of a diameter larger than the projectile in which rifling is not present. See Bullet Jump. See Throat.
Related Terms: BULLET JUMP, THROAT
FREE RIFLE STOCK
A target rifle stock used for position shooting matches. The word “free” refers to the fact that there are no restrictions on its configuration or weight.
FRICTION RING
A metallic ring surrounding the magazine tube to retard the opening velocity of a recoil operated shotgun.
FRONT SIGHT
Any form of sighting device at or near the muzzle of a firearm.
FRONT SIGHT HOOD
A cover to protect the front sight from damage.
Also Known As: Sight Cover
FRONT STRAP
The exposed metal strip at the front of a pistol or revolver grip.
Also Known As: Strap
FULL LENGTH RESIZING
The operation of reforming a fired cartridge case to approximately its original dimensions.
FULL LENGTH SIZING
The operation of reforming a fired cartridge case to approximately its original dimensions.
FULL METAL JACKET BULLET
A projectile in which the bullet jacket encloses most of the core with the exception of the base. Also called Full-Jacketed, Full Patch, Full Metal Case.
Also Known As: Full Metal Jacket, Full Jacketed Projectile, Metal Cased Bullet, Metal Patched Bullet
FULL-COCK
The position of the hammer or striker when the firearm is ready to fire.
FUSED SHOT
Two or more shot pellets joined together during the process of manufacturing or during firing.
GAIN TWIST
Barrel rifling in which the rate of twist is faster at the muzzle than at the chamber end.
GAS CHECK
1. A metallic cup attached to the base of some lead alloy bullets. 2. An obturating cup used under the piston in crusher pressure testing.
GAS CHECK BULLET
A lead alloy bullet with a cup pressed over the heel. Usually copper or gilding metal.
GAS CUTTING
An erosive effect in a firearm caused by the high velocity, high temperature propellant gases.
GAS OPERATED ACTION
An automatic or semiautomatic type firearm in which the propellant gases are used to unlock the breech bolt and then to complete the cycle of extraction and ejection. This is accomplished usually in conjunction with a spring which returns the operating parts to battery.
Also Known As: Gas Operated
GAS PISTON
The component in a gas-operated firearm upon which the propellant combustion gas impinge to operate the action.
GAS PORT
An opening in the wall of a barrel or chamber to allow the redirection of propellant gas. Usually associated with gas-operated actions or other mechanisms.
Also Known As: Ported Barrel, Gas Orifice
GAS VENT
1. Any hole in the action of a firearm to allow the escape of gases from the breech. 2. A hole in the gas cylinder of a firearm to bleed off gas. 3. Ammunition: See Flash Hole. 4. See Barrel Vent.
Related Terms: BARREL VENT, FLASH HOLE
GAUGE
1. A term used in the identification of most shotgun bores. (410 bore is an exception.) It is related to the number of bore diameter lead balls weighing one pound. 2. An instrument for measuring or testing a parameter.
GILDING METAL
A copper alloy with a nominal composition of 95 percent copper and 5 percent zinc. “Gilding Metal” is the trade name for the Copper Development Association, Inc. Alloy C21000. It is extensively, but not exclusively used in the manufacture of bullet jackets. See also “Commercial Bronze.”
GLASS BEDDING
The application of a mixture of fiberglass and resin between the action and/or barrel and stock.
GLOBE FRONT SIGHT
A form of front sight usually used on target rifles generally cylindrical in shape and arranged to accept various inserts containing either rings or posts.
GRAIN
1. A unit of weight (avoirdupois), 7000 grains per pound. The grain unit is commonly used in American and English ammunition practice to measure the weight of components. 2. A term sometimes applied to a single particle of propellant powder. More properly called a kernel or granule.
GRIP
1. In handguns, the handle. 2. In shoulder arms, that portion of the stock to the rear of the trigger.
GRIP ADAPTER
A filler piece attached to the front of the grip of a firearm.
GRIP SAFETY
An auxiliary device on the grip of some handguns which is intended to prevent firing until depressed.
GROOVE DIAMETER
The major diameter in a barrel which is the diameter of a circle circumscribed by the bottom of the grooves in a rifled barrel.
GROUP
A series of consecutive shots fired at the same aiming point without changing the sight adjustments of the firearm.
GROUP SIZE
The determination of the statistics of a particular group. Examples of measurements include Extreme Spread, Mean Radius, Vertical and Horizontal Extreme Spread, to name a few.
Also Known As: Accuracy
GUARD SCREW
A screw that extends from the trigger guard into and through the stock.
GUN COTTON
Nitrated cellulose (either cotton linters, wood pulp or a mixture of the two) which is used for the manufacture of smokeless propellant. Chemical name – nitrocellulose.
GUN POWDER
A commonly used term for cartridge and muzzle loading propellant.
GUN ROOM
A room that is maintained for the purpose of keeping guns in storage, on display, or for repair.
HAIR TRIGGER
A slang term for a trigger requiring very low force to actuate. Sometimes used to describe the light pull of a second trigger in a double set trigger mechanism.
HALF COCK
The position of the hammer, when about half retracted and held by the sear, intended to prevent release of the hammer by a normal pull of the trigger. This can be the safety or loading position of many guns.
HALF COCK SAFETY
The position of the hammer, when about half retracted and held by the sear, intended to prevent release of the hammer by a normal pull of the trigger. This can be the safety or loading position of many guns.
Also Known As: Half Cock
HALF STOCK
A rifle stock with a fore-end which extends approximately to the midpoint of the barrel.
HAMMER
A component part of the firing mechanism which strikes the firing pin or primer sometimes through one or more transfer members. A firearm may have a concealed hammer or an exposed hammer.
HAMMER BLOCK
A device intended to isolate the hammer from the firing pin except when the trigger is pulled.
HAMMER FORGED
The process of forming the interior and/or exterior shape of the barrel of a firearm by pneumatic or hydraulic hammers. Also called Hammered Barrel; Hammered Forged Rifling, Hammer Forged.
Also Known As: Hammered Barrel, Hammered Rifling, Swaged Rifling, Hammer Rifling, Barrel Swaging
HAMMER NOSE
That part of the hammer which serves as the firing pin.
HAMMER NOTCH
One or more grooves in the outer surface of a hammer which interface with the hammer or sear.
HAMMER SPUR
The knob or extension on an exposed hammer which acts as a cocking or decocking aid.
HAMMER STRUT
A component part of some firing mechanisms which is connected between the hammer and the trigger and which acts to move the hammer to the firing position when the trigger is pulled. Also refers to a strut which guides a mainspring to power a hammer.
Also Known As: Strut
HAMMERED RIFLING
The formation of the helical grooves in the bore of a rifle barrel by means of an internal mandrel and external hammers. Sometimes called “Hammer Forged Rifling”.
Also Known As: Swaged Rifling, Hammer Rifling, Hammer Forged Barrels
Related Terms: HAMMER FORGED
HAMMERLESS
Any firearm having a concealed hammer or striker.
HAND
The lever that rotates a revolver cylinder. Sometimes called a Pawl or Dog.
Also Known As: Pawl, Dog
HAND CHECKERING
A process of wood carving gun stocks by hand rather than machine.
HAND STOP
An attachment beneath the fore-end or forearm of a target rifle to restrict the forward movement of the hand. Often also used to attached a target sling.
Also Known As: Knuckle Buster
HAND TRAP
A small, hand-operated target throwing device.
HANDGUN
A firearm designed to be held and fired with one hand.
HANDLOADING
The process of manually assembling a cartridge from component parts (casing, primer, propellant and bullet or wads and shot).
Related Terms: RELOADING
HEAD
The end of the cartridge case in which the primer or priming is inserted and the surface upon which the headstamp identification is imprinted.
HEAD CLEARANCE
The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.
HEADSPACE
The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats. 1. BELT: A type of chamber design in which the cartridge seats in the chamber on an enlarged band ahead of the extractor groove of the cartridge body. 2. MOUTH: A type of chamber design in which the cartridge seats in the chamber on the mouth of the cartridge case. 3. RIMLESS: A type of chamber design in which the cartridge seats in the chamber on the shoulder of the cartridge case. 4. RIMMED: A type of chamber design in which the cartridge seats in the chamber on the rim or flange of the cartridge case.
HEADSPACE GAUGE
A device used in a firearm to determine the distance between the breech face and the chamber surface on which the cartridge seats. Also called Breeching Plug.
Also Known As: Breeching Plug
HEADSTAMP
Numerals, letters and symbols (or combinations) stamped into the head of a cartridge case or shotshell to identify the manufacturer, caliber or Gauge, and other additional information.
HEEL
1. The part of a rifle or shotgun stock at the top of the butt end. 2. The rear portion of a bullet.
HEEL CAVITY
A recess in the base of a bullet.
HEELED BULLET
A bullet design where the portion of the bullet exterior to the shellcase has the same diameter as the case, and steps down to a narrower “heel” portion that fits inside the case.
HIGH BASE
The term commonly applied to a shotshell with a high metal cup, but properly applies to the height of the internal base wad. Often misused as synonymous with high brass or high cup.
HIGH BRASS
Common terminology referring to the length of the external metal cup on a shotshell. See High Cup
Related Terms: HIGH CUP
HIGH CUP
Correct term for shotshells having a high metal head type of construction.
Related Terms: HIGH BRASS
HINGE PIN
A cylindrical member at the forward end of a frame about which the barrel or barrels pivot. Also called a Joint Pin.
Also Known As: Joint Pin
HINGED FRAME ACTION
An action in which the barrel(s), one or more being either smooth or rifled, is pivoted on the frame. When the action is open, the barrel may pivot up or down or sideways for loading or unloading. When the action is closed, the breech of the barrels swings against the standing breech. Opening is normally accomplished by movement of a top, side, or under lever. A top break action is an example of a hinged frame action.
HINGED OR FOLDING TRIGGER
A trigger which is hinged to fold forward.
HOLLOW BASE BULLET
A bullet with a deep heel cavity.
HOLLOW POINT BULLET
A bullet with a cavity in the nose to facilitate expansion.
Also Known As: Open Point Expanding Bullet
Related Terms: EXPANDING BULLET
HOODED SIGHT
A front sight that is provided with a cover to shade it from direct light.
Also Known As: Sight Cover
HOOK OF LUMP
A notch machined into a lump used to mate with the hinge pin.
HORIZONTAL DISPERSION
The greatest horizontal distance between any two bullet holes on a target, normally measured center-to-center.
HULL
A slang term for a cartridge or shotshell case.
IGNITION TIME
The elapsed time from moment of firing pin contact on the primer to the point on the X (time) axis equal to the point where the pressure time curve indicates propellant burning has initiated.
IMPRESSED CHECKERING
A heated die process which produces a carved effect in the gun stock or forearm.
IMR POWDER
The abbreviation for Improved Military Rifle Powder. A single base, tubular, smokeless propellant.
IN BATTERY
A firearm is said to be “In Battery” when the breeching mechanism is in the proper position for firing.
IN LINE
A firearm design incorporating it’s firing mechanism substantially in line with the longitudinal axis of the barrel. Ignition gases are typically induced concentric to the bore with this design.
INDUSTRIAL CARTRIDGE
1. Usually a blank cartridge used in industrial applications such as stud drivers. Usually color coded to indicate power level. Also referred to as power tool cartridges and power actuated tool cartridges. 2. 8 Gauge industrial loads with single projectiles or buckshot used for cleaning continuous cement kilns and other industrial applications.
Related Terms: POWDER ACTUATED TOOL, POWER DEVICE CARTRIDGE
INERTIA BLOCK
1. A device intended to function during recoil to set the fire control mechanism to fire a second barrel. 2. A device intended to function during recoil to prevent doubling on some double barrel shotguns.
INERTIA BULLET PULLER
A tool using impact to remove a bullet from a cartridge case.
INERTIA FIRING PIN
A design in which the striker or hammer stops after hitting the firing pin, requiring the firing pin reach the primer under its own inertia.
INERTIA OPERATED ACTION
A self-loading type firearm in which components of the locking system remains relatively stationary while the rest of the firearm recoils and thereafter unlocks the breech bolt to complete the cycle of extracting, ejecting and reloading.
Also Known As: Inertia Operated
INERTIA TRIGGER
The term used for firearms having two barrels and a single trigger wherein the inertia resulting from the recoil forces of firing one barrel causes the trigger sear to switch to the unfired barrel. A second pull of the trigger can then fire the second barrel.
INSIDE LUBRICATED BULLET
A bullet having lubrication in grooves on the bearing surface of the projectile. When seated, these grooves are covered by the cartridge case.
INSTRUMENTAL VELOCITY
The velocity of a projectile, or a shot charge, that is recorded by suitable instrumentation located a predetermined distance from the muzzle of a test barrel or a firearm.
INTERCHANGEABLE BARREL
Barrels which may be installed on a particular action without factory fitting.
INTERIOR BALLISTICS
The science of ballistics focusing on all thermochemical and physical events from primer ignition through projectile exit from the muzzle.
IRON FORE-END
On firearms with a one-piece stock, an intermediate part that holds the wood against the barrel and frame and retains the latch mechanism.
IRON SIGHT
Any sight, front or rear, not containing optical magnifying elements. It may be fixed or adjustable. Also called Metallic Sight.
Also Known As: Metallic Sight
JAM
A malfunction of a firearm that prevents the action from operating; may be caused by faulty parts, ammunition, improper maintenance or improper use of the firearm.
JANKA HARDNESS, JANKA TEST
A system of rating the hardness of wood by use of a 0.444 inch diameter ball; measured in pounds required to force one half the diameter of the ball into the wood.
JIG
A precise mechanical locating device used in production of component parts and/or assembly of firearms.
JOINT
A place where two or more parts come together so as to permit motion. The term is sometimes used in reference to the pivot point of a hinged action.
Also Known As: Hinge
JUG CHOKE
A type of shotgun barrel choke, wherein a slight recess is formed in the bore approximately one inch behind the muzzle. The recess causes the shot to gather before leaving the muzzle resulting in a denser pattern.
Also Known As: Tula Choke
JUMP
The upward and rearward recoiling movement of a firearm when it is fired. See Bullet Jump. See Recoil.
Related Terms: BULLET JUMP, RECOIL
KEEL
A spacer used to maintain center distance of double barrels during manufacture.
KEEPER
A means of holding straps or cords, such as gun slings, together with a loop or clip made of leather, metal or plastic.
KERNEL
A single particle of propellant powder.
KEYHOLE / KEYHOLING
An oblong or oval hole in a target that is produced by an unstable bullet striking the target at an angle to the bullet’s longitudinal axis.
KICKER
The part which draws back a rod which forces home a cartridge on some recoil operated firearms. Also refers to some break-open shotgun ejectors.
KINETIC ENERGY (FORMULA)
Based on the general equation for kinetic energy, Ek=½mv2, which directly uses mass (m) and velocity (v), the following formula is used to calculate the kinetic energy of a projectile (expressed in foot-pounds):
E=(W*V2)/(14000*gc).
In this formula, W = weight of projectile, in grains; V = velocity, in feet per second; gc= gravitational constant, 32.174 ft/s2
KNUCKLE
The front section of the action bar flats.
KNURL, KNURLING
1. A series of regular ridges or rectangles on a metal surface to help prevent slipping. Used on triggers, hammers, bolt handles, etc. 2. Sometimes used in referring to cartridge case or bullet cannelures.
LAMINATED CASE
A scaly appearing area indicative of lamination caused by contamination of cartridge case brass.
LAMINATED STOCK
A stock which is made from two or more pieces of wood which have been glued together longitudinally.
LAND, LANDS
The uncut surface of the bore of a rifled barrel.
LANYARD
A strap or cord that is attached to a firearm (usually handgun) and worn around the neck or shoulder to prevent loss of the firearm.
LAP
The process of polishing a metal surface such as the interior of a barrel with a fine abrasive substance.
Also Known As: Lapping
LATCH
A movable device used to secure a part or piece in place relative to another. As applied to firearms, various types of latches are employed to hold barrels, cylinders, etc., in position and to enable these parts to be moved for loading, unloading and disassembly.
Also Known As: Bolt
LEAD BULLET
A bullet formed by a lead alloy.
LEAD KNIFE GROOVE
A circumferential impression in a lead bullet applied forward of the mouth of the case after crimping.
LEAD SHOT
Spherical pellets used in loading shotshells. Commonly formed from lead but may be made from steel.
Also Known As: Drop Shot, Chilled Shot
LEADING
The accumulation of lead in the bore of a firearm from the passage of lead shot or bullets. Also called Metal Fouling.
Also Known As: Metal Fouling
LENGTH OF PULL
See Stock Dimensions.
LENGTH OF STOCK
See Stock Dimensions.
LEVER
A projecting piece used to operate a mechanism, as the lever of a lever action firearm. See also, Lever Action.
Related Terms: LEVER ACTION
LEVER ACTION
An action in which an external lever generally below the receiver, cycles the breech bolt on a horizontal or nearly horizontal plane in line with the barrel.
LEVER LOCK
A device intended to hold the lever closed on some lever action guns.
LIGHT BLOW
Insufficient firing pin energy or protrusion resulting in failure to ignite the primer.
Also Known As: Light Strike, Light Hit
LINE ENGRAVING
A form of engraving in which the entire pattern or design consists of shallow line cuts as opposed to engraving done in bas-relief. This type of engraving is often found on the metal parts of firearms.
LINE OF DEPARTURE
The direction in which a projectile is moving when it leaves the muzzle of a firearm. Also defined as the tangent to the trajectory at the muzzle. See Trajectory.
Related Terms: TRAJECTORY
LINE OF SIGHT
A straight line drawn from the shooter’s eye, passing through the sights of a firearm and extending from the firearm to a target.
LINK
1. A part in a firearm that connects two other parts, while permitting flexibility between the parts. 2. The individual interlocking pieces that form the belt for belted ammunition.
LINKAGE
A connection between parts used to transmit motion from one to the other.
LIPPED-MOUTH
If a bullet is incorrectly inserted into the mouth of a case, it may deform the case mouth rearward, downward, causing a defect. Also known as a Tear-Down.
Also Known As: Tear-Down
LIVE AMMUNITION
A metallic cartridge or shotshell that is complete and ready to use.
Also Known As: Fixed Ammunition
LOAD
1. The combination of components used to assemble a cartridge or shotshell. 2. The act of putting ammunition into a firearm.
LOADING BLOCK
A device containing a number of blind holes into which cases or completed ammunition are placed.
LOADING DENSITY
The relationship, in a cartridge, of the volume of the propellant to the available case volume. Usually expressed as a percentage.
LOADING GATE
1. Revolvers: A hinged piece attached to the frame which is opened to permit loading. 2. Shoulder Arms: A spring loaded cover for the loading port.
LOADING PORT
The opening in a receiver where a cartridge may be placed in the firearm either directly into the chamber or the magazine.
LOADING RAMP
A platform or cut placed in the bottom of the receiver that aids in guiding a cartridge into the chamber as the action is closed.
LOCK
1. A general term referring to the total firing mechanism in a firearm. 2. Range command sometimes used to indicate engagement of a manual safety (“Lock your firearms”). 3. An accessory intended to help secure a firearm from unauthorized use.
Also Known As: Gun Lock
LOCK ENERGY
The amount of energy delivered to the primer from the firing pin blow.
LOCK FRAME
A device incorporated into the mechanism of some firearms where the barrel and the bolt assembly recoil upon firing. The lock frame acts to absorb the shock of the recoiling parts prior to the bolt unlocking and opening.
LOCK PLATE
A metal plate mounted on the stock of a gun to provide for mounting of, or access to, the firing mechanism.
LOCK-TIME
The time interval between sear release and the firing pin striking the primer.
LOCKED BREECH ACTION
An action in which the breech bolt is locked to the barrel or receiver, until unlocked through a mechanical process.
LOCKING BLOCK
The firearm component designed to secure the action in the locked position.
Also Known As: Locking Bolt
LOCKING CAM
An incline, either helical or straight, to assist in closing the action on a chambered cartridge.
LONG RIFLE
1. Originally, the term was used in reference to long-barreled flintlock rifles. 2. The name given one type of a caliber 22 rimfire cartridge.
LOOSE PRIMER
A primer which does not fit properly in the primer pocket of a cartridge case or shotshell.
LOT OF POWDER
A homogeneous blend of powder having defined chemical and physical properties, as well as performance characteristics.
LOW BASE
A term commonly applied to a shotshell with a low metal cup, but properly applies to the height of the internal base wad. Often misused as synonymous with low brass or low cup.
LOW BRASS
Common terminology referring to the length of the external metal cup on a shotshell.
Also Known As: Low Cup
LOW CUP
Correct term for shotshells having a low metal head type of construction.
LUBRICATED CARTRIDGE
See specific type: Bullet, Inside Lubricated Bullet, Outside Lubricated.
LUBRICATION GROVE
A circumferential groove in a projectile for the purpose of holding lubrication.
LUMP
One of several projections located on the underside of the barrel or barrels on break action guns, which serves to secure the barrels to the action or receiver. See Barrel Lug.
Related Terms: BARREL LUG
LUP (LEAD UNITS OF PRESSURE)
(Obsolete) A pressure value determined by means of lead crusher cylinders.
MACHINE CHECKERING
A process of wood carving gun stocks by machine rather than by hand.
MACHINE GUN
A fully automatic firearm that loads and fires live cartridges and ejects the spent cartridges continuously when the fire mechanism is held until ammunition is exhausted, the firearm’s designed burst cycle is completed or the firing mechanism is released.
Also Known As: Full Automatic
MACHINE REST
Mechanical apparatus used for holding a firearm in a precisely controlled, selected position for testing the accuracy of the ammunition or the firearm.
MAGAZINE
1. A building for the storage of either ammunition or its components. 2. A receptacle for a firearm that holds a plurality of cartridges or shells under spring pressure preparatory for feeding into the chamber. Magazines take many forms, such as box, drum, rotary, tubular, etc. and may be fixed or removable.
MAGAZINE CATCH
The device that retains or releases the magazine in a firearm. Also known as Magazine Latch or Magazine Release.
Also Known As: Magazine Latch, Magazine Release, Magazine Lock
MAGAZINE CUT OFF
A mechanical device that enables the user to selectively enable or disable the magazine feed mechanism of a firearm.
Also Known As: Cut Off
MAGAZINE FED
A repeating firearm in which the ammunition for subsequent firing is fed from a magazine.
MAGAZINE FOLLOWER
A spring-actuated device to move cartridges in a magazine into the feeding position.
MAGAZINE PLUG
1. A part inserted in a magazine to reduce its capacity. 2. A part in the end of a tubular magazine which closes the end and retains the spring.
MAGAZINE SPRING
The spring in a magazine that exerts its thrust against the follower.
MAGNUM
A non-technical term commonly used to imply higher performance than standard cartridges or shells of a given caliber, or gauge or similar cartridges. Rifles, handguns or shotguns that are designed to fire Magnum cartridges or shells may also be described with the term Magnum.
Also Known As: Magnum Cartridge
MAINSPRING
The mechanical, energy storage device that operates the striker or hammer of a firearm.
MALFUNCTION
Failure of a firearm to perform properly due either to the firearm or the ammunition.
MANNLICHER MAGAZINE
A type of rotary magazine.
MANNLICHER STOCK
A full length rifle stock which extends from the butt to the muzzle.
MANUAL SAFETY
A safety device on some firearms that must be manually engaged and subsequently disengaged to permit normal firing.
MARK
A term used in conjunction with a number to designate a specific model or type of firearm or ammunition.
Also Known As: M, Mk
MARKINGS
Words or symbols, stamped, rolled, cast or engraved, on a firearm designating the manufacturer, model, origin, caliber or gauge, choke, material, etc.
MATCH AMMUNITION
Ammunition made specifically for match target shooting. Produced with special controls to assure maximum uniformity of cartridge performance.
MATTE
A dull non-reflecting metallic surface.
Also Known As: Matte Finish
MAXI BALL
An elongated, heavy weight bullet, usually incorporating annular exterior grooves to hold lubricant.. Designed to be loaded and fired without a patch, it’s major diameter being slightly larger than bore diameter causing engraving by the rifling upon loading.
MAXIMUM CHARGE
The greatest charge weight, in grains, of a particular propellant that may be used with other specified ammunition components without exceeding the safe, maximum, allowable pressure limit for the specific cartridge or shell being loaded.
MAXIMUM RANGE
The greatest distance a projectile can travel when fired at the optimum angle of elevation of the gun barrel.
MEAN RADIUS
The arithmetic mean of the distances between the centers of each shot hole from the calculated group center.
MECHANICAL TRAP
A mechanically operated clay target throwing device.
MEPLAT
A term for the blunt tip of a bullet, specifically the tip’s diameter.
METAL FOULING
Metallic bullet material left in the bore after firing.
METALLIC AMMUNITION
A generic term for rimfire and centerfire ammunition derived from their metallic cases.
METALLIC CARTRIDGE
Ammunition having a metallic cartridge case.
METFORD RIFLING SYSTEM
A form of rifling with shallow grooves that are arcs of less than half of the groove diameter.
MICROMETER POWDER MEASURE
An adjustable, volumetric device for measuring propellant powders.
MICROMETER SIGHT
A sight with a mechanism for adjusting windage and elevation settings controlled by cylindrically calibrated knobs, usually with detents to control and indicate setting intervals.
MID-RANGE
1. A term that defines a specific point in the trajectory of a projectile that is half the distance between the firearm and the target. 2. A reduced velocity, centerfire cartridge, used principally in target shooting.
MID-RANGE TRAJECTORY
The distance, measured in inches, that a projectile travels above the line of sight at a specific point in the trajectory that is half the distance between the firearm and a target.
MIDDLE SIGHT
A second, smaller bead sight near the middle of the barrel or barrels of some shotguns.
Also Known As: Mid Bead Sight
MIL
The angle subtended by one unit at 1000 units.
MINIE BALL
A conical nosed lead bullet, slightly under bore diameter, incorporating a hollow base, designed to expand into the rifled bore upon firing for gas sealing purposes without the use of a patch.
MINUTE OF ANGLE (M.O.A.)
An angular measurement method used to describe accuracy capability. A minute of angle is one sixtieth of a degree, and subtends 1.047 inches at 100 yards, which for practical shooting purposes is considered to be one inch. A minute of angle group, therefore, equals one inch at 100 yards, two inches at 200 yards, etc.
MIRAGE
A visual phenomenon that appears to displace a target from its true position through a shimmering effect. It is caused by heated air that deflects light rays.
MISFEED
Any malfunction during the feed cycle of a repeating firearm resulting in the failure of a cartridge or shell to enter the chamber completely. Also known as Failure to Feed.
Also Known As: Failure to Feed
MISFIRE
A failure of the priming mixture to be initiated after the primer has been struck an adequate blow by a firing pin or the failure of the initiated primer to ignite the powder.
MONOBLOC
The solid section at the breech end of some multi-barrel guns into which the barrels are inserted.
MONTE CARLO STOCK
A stock with a raised comb to bring the eye in alignment with the sight.
Also Known As: Monte Carlo
MOUTH
The open end of a cartridge case or shotshell, from which the projectile or shot charge is expelled in firing.
MULLERING TOOL
A type of checkering tool.
MULTIPLE LEAF SIGHT
A type of open, rear sight having more than one folding leaves. It may also have one fixed leaf.
Also Known As: Three Leaf Sight
MUSHROOM
A descriptive term for the post-impact profile of a bullet that is designed to expand upon striking a target.
MUSHROOM BULLET
A bullet that has expanded upon impact into a mushroom-like shape.
MUSHROOMING
The act of expansion of a bullet upon impact with a target.
MUSKET
Military firearm with long barrel and fore-end or forearm extending nearly to muzzle.
MUSKET CAP
The ignition source for most military muzzle loading rifles of the Civil War era, usually consisting of a copper alloy cup containing the priming mix. They are larger than percussion caps and typically incorporate a continuous or segmented flanges (Wings) at the cup mouth for ease of handling.
MUZZLE
The end of a gun barrel from which the bullet or shot emerges.
MUZZLE BLAST
The resultant noise that occurs at the muzzle of a firearm when the projectile leaves the muzzle and hot gases are released.
MUZZLE BRAKE
A muzzle attachment or feature that uses the propellant combustion gas with the desired effect of redirecting the recoil.
MUZZLE CAP
A cover put on the muzzle end of a barrel to keep out foreign matter.
MUZZLE ENERGY
A projectile’s energy at the time it leaves the muzzle of a gun.
MUZZLE FLASH
The illumination which is the result of the expanding gases from the burning propellant particles emerging from the barrel behind the projectile and uniting with oxygen in the air.
MUZZLE GUARD
A device put on the end of a barrel with a hole concentric with the bore to admit a cleaning rod and keep the rod from wearing the rifling in this critical area. Not used on guns cleaned from the breech end.
MUZZLE JUMP
The generally upward motion of the muzzle of a firearm which occurs upon firing.
MUZZLE LOADER
Any firearm into which the projectile(s) and, usually, propellant charge are loaded from the muzzle of the barrel, or the front end of the cylinder for muzzle loading revolvers.
MUZZLE VELOCITY
The velocity of a projectile as it exits the muzzle of a firearm.
MUZZLE WAVE
The air that is compressed and moves out radially from the muzzle of a firearm after firing a projectile.
MUZZLE–BREAK
An electrical or optical device which signals the passage of shot or a projectile at the muzzle of a firearm.
NATIONAL MATCH AMMUNITION
Ammunition produced for the American National Matches (at Camp Perry, Ohio) by appropriate government or commercial manufacturing facilities. Cartridges are usually, but not always, head-stamped “NM” for identification purposes.
NATIONAL MATCH BULLET
A bullet manufactured specifically for ammunition issued to competitors at the National Matches.
NATO CARTRIDGE
A common designation for military cartridges produced under the specifications of the North Atlantic Treaty Organization.
NECK ANNEALING
A heating process used in cartridge case manufacture intended to relieve internal stresses in the neck area caused by cold working.
NECK CLEARANCE
The dimensional difference between the diameter of the neck of a loaded cartridge case and the chamber.
NECK OF CARTRIDGE
The reduced diameter cylindrical portion of a cartridge case, extending from the bottom of the shoulder to the case mouth.
Also Known As: Neck, Case Neck
NECK RADIUS
The curved surface between the neck and the shoulder of a cartridge case.
NECK SIZING
The operation performed by reloaders to reduce or restore the original neck diameter of a fired cartridge.
NECK TENSION
The circumferential stress that the case neck exerts on the seated bullet, as a result of the interference fit provided by the case neck inside diameter and the bullet outside diameter.
NECK THICKNESS
Average thickness of the wall of a cartridge case surrounding the bullet.
NECKING-DOWN
The use of case forming dies to reduce both the outside and inside diameter of a cartridge case neck.
NIPPLE
A hollow, cone-shaped part of a percussion firearm upon which a percussion cap or musket cap is placed. The hole in the nipple directs the flame or flash of the cap to the powder charge. Also called a Cone.
NIPPLE PICK
A pointed instrument used to clean the orifice of nipples on percussion firearms.
NIPPLE WRENCH
Tool made for the removal and installation of nipples on percussion firearms.
NITRO WAD
An unlubricated, overpowder wad made of cardboard or felt. It is used with smokeless powder. Also called Nitro Card Wad.
Also Known As: Nitro Card Wad
NITROGLYCERINE
The common term for the nitric acid ester of glycerine, i.e., glyceryl nitrate. It is incorporated with nitrocellulose smokeless powder formulations to make double base propellant powders. See Double Base Powder.
Related Terms: DOUBLE BASE POWDER
NOMINAL CHARGE
A typical charge weight of a specific powder for a specific combination of components.
NON-CORROSIVE
A term applied to primers that contain no chemical compounds that could produce corrosion or rust in gun barrels, but does not necessarily protect from corrosion or rust.
NON-CORROSIVE PRIMER
A primer which does not contain chemical compounds that could produce corrosion or rust in gun barrels. It does not by itself prevent corrosion or rust.
NON-HYGROSCOPIC POWDER
Smokeless powder which resists water absorption.
NON-MERCURIC PRIMER
A primer which does not contain compounds of mercury.
NON-SELECTIVE SINGLE
A single trigger on double-barrel guns which fires the barrels in a fixed sequence.
NOSE
The point or tip of a bullet.
NOTCH SIGHT
An Open rear sight having either a “V,” “U” or square shaped cut on its upper edge.
OBTURATION
The momentary expansion of a cartridge case against chamber walls which minimizes the rearward flow of gases between the case and the chamber wall when the cartridge is fired.
OFFSET MOUNT
A mount for telescopes or iron sights affixed to the gun in such a manner, that the line of sight is to the side and above the receiver or barrel.
OFFSET STOCK
A curved buttstock for use by a shooter who wishes to use the left eye when shooting right handed or vice versa. Also known as a Cross-Over Stock.
Also Known As: Cross-Over-Stock
OGIVE
The curved portion of a bullet forward of the bearing surface.
OGIVE BULLET
The curved forward part of a bullet.
OILPROOF
The treatment of a cartridge to minimize the entry of oil or water.
ONE PIECE MOUNT
A mount for a telescopic sight that consists of a one piece base as opposed to a two piece base.
ONE PIECE SHOTSHELL
1. A shotshell component having the body and basewad as a single unit with a metallic cup. Sometimes called Unibody Shell. 2. A complete round of ammunition having the body and basewad as a single unit without a head of a different material.
Also Known As: Unibody Shell, Integral Base Wad
ONE PIECE STOCK
A full length stock made from a single piece of wood. Includes both the butt and fore-end.
OPEN BREECH ACTION
An action in which the breech bolt is held open until the trigger is pulled.
Also Known As: Open Bolt Action
OPEN POINT
A type of bullet having a cavity in the tip or nose.
OPEN SIGHT
A rear sight having a notch through which the front sight is aligned for aiming.
OPERATING HANDLE
Handle of semi or full automatic firearm used to cycle firearm without firing. Also called Charging Handle, Cocking Handle, Cocking Knob.
Also Known As: Charging Handle, Cocking Handle, Cocking Knob
OPERATING LEVER
On lever action firearms that part operated by the hand to open and close the breech.
Also Known As: Finger Lever
OPTICAL SIGHT
A sight containing optical elements which may magnify the target.
ORANGE PEEL
A rough textured finish similar to the skin of an orange, generally referring to certain stock finishes.
ORIFICE
A small hole or vent such as the gas port in the barrel of a gas-operated firearm.
Related Terms: GAS PORT
ORIGIN OF TRAJECTORY
When a bullet exits from the barrel of a firearm, the location of the center of the bore at that specific point in time is called the origin of the trajectory.
OUT-OF-BATTERY
The condition of the breeching mechanism of a firearm not being completely locked or completely closed.
OUTSIDE LUBRICATED BULLET
A lead bullet lubricated on the surface not covered by the cartridge case.
OVER AND UNDER
Firearms with two barrels placed one above the other.
OVER-BORE
A shotgun barrel bore diameter greater than the SAAMI maximum for that gauge. Also called a Baker Bore.
Also Known As: Baker Bore
OVER-BORE CAPACITY
The point where the powder charge of a particular burning rate of propellant exceeds the capacity of a barrel of specific caliber and length to convert the propellant gas pressure to velocity.
OVERALL LENGTH
1. Firearm: The dimension measured parallel to the axis of the bore from the muzzle to a line at right angles to the axis and tangent to the rearmost point of the butt-plate or grip.
2. Ammunition: The greatest dimension of a loaded cartridge, i.e., from face of the head to the tip of the bullet for centerfire or rimfire or to the crimp for shotshells or blanks (not to be confused with the uncrimped length in a shotshell.)
OVERPOWDER WAD
Various designs of separators, made of various materials and used between the propellant powder and the shot pellets.
OVERTRAVEL
The distance after a particular event occurs in the normal operation of the firearm, e.g. additional rearward motion of the trigger after sear or hammer release.
PALM REST
An adjustable support for a target rifle extending downward from the forearm.
PAPER DISC
Small circular piece of treated paper cut and pressed into the primer cup in contact with the priming mixture. Also called Foil.
Also Known As: Foil
PAPER SHELL
Shotshells which are constructed with a body made from paper tubing.
Also Known As: Paper Shotshell
PARKERIZING
A non-reflecting, rust-resistant finish used on metal surfaces of some firearms. Also called Phosphatizing or Phosphate Coating.
PARTITION BULLET
A bullet designed for controlled expansion having a jacket which is divided into two cavities which enclose the forward and rear cores of the bullet. It is designed so the first cavity expands and the rear cavity holds together for penetration.
PATCH
1. A piece of cloth used with a rod to clean the bore of a firearm.
2. A piece of paper wrapped around lead bullets to prevent leading of the barrel and to improve the gas seal.
3. In muzzleloading firearms, the piece of cloth surrounding the bullet or ball to improve the gas seal.
PATCHED BALL
1. For modern cased ammunition, the term patched ball refers to a full metal jacketed bullet (FMJ). 2. For muzzleloading, the term refers to round or conical lead projectiles that utilize cloth or other material which acts as a gas seal or a guide for the projectile. 3. Early fixed ammunition using paper as a gas seal for the projectile.
PATRIDGE SIGHT
A rear sight on pistols or revolvers having a flat top with a square notch used with a broad flat-topped front sight. Named after E. E. Patridge.
PATTERN
The distribution of individual pellets fired from a single shotshell in a shotgun. Generally measured as a percentage of the total number of pellets striking within a 30” circle at 40 yards. Some skeet guns are measured using a 30” circle at 25 yards.
PEAK PRESSURE
That maximum instantaneous pressure measured in the chamber of a firearm, produced by the expanding propellant combustion gases.
PEEP SIGHT
Common, popular term for aperture rear sights.
Also Known As: Receiver Sight
PELLET (PROJECTILE)
1. A common name for the small spherical projectiles loaded in shotshells.
2. A non-spherical projectile used in some air rifles.
PENETRATION
Travel of a bullet or shot pellet into the target medium.
PERCUSSION
A means of ignition of a propellant charge by a mechanical blow against the primer (modern) or cap (antique).
PERCUSSION CAP
A small, generally cylindrical, metallic cup containing primer mix used to ignite the main powder charge in some muzzle-loading firearm designs.
PERCUSSION COMPOSITION
A combination of explosive and/or pyrotechnic-type ingredients, which, when pressed into a percussion cap, will ignite upon sufficient impact from a hammer or striker and, in turn, initiate the propellant in a muzzle loader.
PIERCED PRIMER
A fired primer which has been perforated by the firing pin.
Also Known As: Punctured Primer
PIEZOELECTRIC PRESSURE TRANSDUCER
A device which generates an electrical charge that is proportional to the pressure applied to its crystal element.
Also Known As: Pressure Transducer
PISTOL
A firearm intended to be fired with one hand in which the chamber(s) are integral to the barrel(s).
PISTOL GRIP
On shoulder firearms, that part of the stock behind the trigger, shaped similar to the grip of a pistol to afford a better grasp.
PISTOL GRIP ADAPTER
An accessory made to attach to the front of a revolver grip to afford a better grasp.
PISTOL GRIP STOCK
A stock or buttstock having a downward extension behind the trigger guard somewhat resembling the grip of a pistol.
PISTON RING
A sharp edged ring mounted on the piston of gas operated automatic and semiautomatic firearms which makes a close seal between the piston and cylinder wall, and by a scraping action reduces the accumulation of carbon in the cylinder.
PIT
A scar on a metal surface usually the result of extensive rusting.
PITCH
1. (Rifling) the distance a bullet must travel in the bore to make one revolution. 2. (Grips) the angle that the front of the handgun grip makes with the line of sight. 3. A component used in making clay targets. 4. See Stock Dimensions.
Related Terms: STOCK DIMENSIONS
PIVOTING BLOCK ACTION
An action in which the breech block pivots in an arc to expose or lock the breech.
PLASTIC SHOTSHELL
A complete round of ammunition having a plastic body, a basewad that may or may not be a single unit and a metallic head.
PLATED BULLET
The entire bullet, or just the jacket, electrolytically plated with a different material.
PLATED SHOT
Copper or nickel-plated shot, coated to increase apparent shot hardness and reduce in-bore shot deformation.
Also Known As: Coated Shot
PLINKING
The informal target shooting at inanimate objects other than paper targets located at arbitrary or indefinite distances from the firing point.
PLUG BULLET
1. A device used in scoring bullet holes in a paper target. 2. A pin inserted in a bullet mold to form a cavity in the nose or base of a bullet.
PLUG SCREW
Screw used to fill holes for sight or telescopic sight mounting when not in use. Also used to fill access holes to internal pins. Also called Dummy Screw.
Also Known As: Dummy Screw
POINT OF IMPACT
The point at which a bullet hits a target.
POINT-BLANK-RANGE
Very close range.
Related Terms: MAXIMUM POINT-BLANK-RANGE
POINT-OF-AIM
The exact point on which the shooter aligns the firearm’s sights.
POINTED PROJECTILE
A projectile that is designed with a pointed profile.
POST SIGHT
A front sight with flat sides and top.
POWDER
Commonly used term for the propellant in a cartridge or shotshell.
POWDER ACTUATED TOOL
A class of tools, such as nail drivers, that use the expansion of propellant combustion gases as their motive force.
Also Known As: PAT
POWDER BURN
A burn that may result from contact with hot powder particles or propellant combustion gases.
POWDER BURNING RATE
The speed with which a propellant burns inside a cartridge case. It is affected by both physical and chemical characteristics, as well as conditions under which the powder is burned.
Also Known As: Burning Rate, Burning Speed
POWDER CHARGE
The amount of powder by weight in a cartridge case or shotshell.
POWDER DETERIORATION
1. (Smokeless Propellant) The degradation of propellant from the decomposition of the explosive components of the propellant. This can be accelerated by improper storage conditions.
2. (Black Powder) The degradation of black powder typically caused by absorption of moisture from the air.
POWDER FOULING
Residue left in firearms after firing, either from unburned propellant or its solid combustion products.
POWDER MEASURE
A device to measure quantities of powder volumetrically.
POWDER MILL
1. The machinery that produces Black Powder to the required geometry. 2. A manufacturing facility that produces powder, classically applied to Black Powder facilities but can be used for Smokeless Propellant manufacturing plants.
POWDER SCALE
A balance or weighing instrument for accurately weighing powder charges.
POWER DEVICE CARTRIDGE
Cartridges designed to accomplish mechanical actions. The cartridges consist of a shellcase and propellant that when ignited produces gases for inflation, linear or rotary motion, activate diaphragms, or project fastening devices. See also, Industrial Cartridge.
Related Terms: INDUSTRIAL CARTRIDGE, POWDER ACTUATED TOOL
PREMATURE FIRING
The improper firing of a cartridge or shotshell before the breech or action of the firearm is fully closed and locked into firing position.
PRESCRIBED LOAD
For every caliber of metallic cartridge and the numerous bullet weights used in each, and for each shotshell gauge or bore, and the various shot weights loaded in each, a particular combination of components should be used. Collectively, the correct components for any given cartridge or shell may be referred to as the prescribed load.
PRESSURE
In a gun or cartridge, the force imparted to various components that is developed by the expanding gases generated by the deflagration of the propellant when fired.
PRESSURE BARREL
A barrel, typically heavy-walled, made in accordance with a standards-setting organization specifications, with appropriate features for the installation of instrumentation to measure pressure.
PRESSURE CURVE
A graph of the relationship of chamber pressure to time or travel in a firearm when a cartridge or shell is fired.
PRESSURE DETERMINATION
The act of measuring the pressure generated in cartridges or shotshells contained in the chamber of a test barrel. See Pressure. See Average Pressure. See Pressure Barrel. See Chamber Pressure. See Pressure Curve.
Related Terms: AVERAGE PRESSURE, CHAMBER PRESSURE, PRESSURE, PRESSURE BARREL, PRESSURE CURVE
PRESSURE ESTIMATION
Attempting to roughly establish pressure of a cartridge by visual observation or measurement of a fired cartridge case.
PRESSURE GAUGE
A piston and crusher system, or a piezoelectric transducer system used to measure internal barrel pressure in a firearm or test device.
Also Known As: Piezo Transducer, Copper Crusher
PRETRAVEL
The initial distance the trigger moves prior to sear movement. Also known as Trigger Take-up or Slack. See Trigger Creep.
Also Known As: Trigger-Take Up, Trigger Slack
Related Terms: TRIGGER CREEP
PRIMER
An ignition component containing explosive mixture in a metallic cup, which provides a source of heat and flame when initiated. Percussion primers utilize mechanical impact for initiation energy and may have an anvil in the cup or the anvil may be integral to the cartridge case. (See Boxer Primer and Berdan Primer.) To a lesser extent, electrically-initiated primers have been used in sporting small arms ammunition and are currently used in some military small arms applications.
Related Terms: BERDAN PRIMER, BOXER PRIMER
PRIMER CRATERING
A circumferential rearward flow of metal surrounding the indentation of a firing pin in a fired primer cup.
Also Known As: Primer Flow-Back
PRIMER CUP
Brass or copper cup designed to contain priming mixture.
PRIMER FLASH
The illumination produced by the extremely hot gases which result from the very rapid build-up of pressure and temperature when the priming mixture detonates.
PRIMER LEAK
The escape of gas between the primer cup and head of the cartridge case, or shotshell head.
PRIMER PELLET
The explosive component of a primer.
PRIMER POCKET
A cylindrical cavity formed in the head of a metallic centerfire cartridge case, or in the head of a shotshell, to receive an appropriate primer or battery cup primer assembly.
PRIMER SEATING
The insertion of a centerfire primer or battery cup in the head of a cartridge case or shotshell. Properly seated, it should be flush or below the face of the head.
PRIMER SETBACK
The condition when a primer, or battery cup primer assembly, moves partially out of its proper location in the primer pocket of a metallic cartridge or shotshell during firing.
PRIMER TUBE
A tube for holding primers in a handloading press.
PRIMING MIX/MIXTURE
A combination of explosive and/or pyrotechnic-type ingredients, which, when pressed into a cup or spun into the rim cavity of a rimfire shell, will ignite upon sufficient impact from a firing pin and, in turn, initiate the propellant in a cartridge or shotshell.
PROGRESSIVE BURNING POWDER
A smokeless propellant in which the burning rate is controlled by physical and/or chemical means.
PROJECTILE
An object propelled from a firearm by the force of rapidly burning gases or other means.
PROJECTILE ENERGY
The kinetic energy of a projectile.
PROJECTILE ROTATION
The spinning motion that is imparted to a projectile due to engagement with the rifling in the barrel of a firearm, as it is driven down the barrel. The rate of rotation is dependent upon the rate of twist of the rifling and the velocity. The barrel twist (left or right) determines the direction of the rotation.
PROOF MARK
A stamp applied at or near the breech or other stressed component of a firearm after it has passed a proof test.
PROOF TEST
The test of an assembled firearm or individual components by firing a Definitive Proof Cartridge. See Definitive Proof Cartridge.
Related Terms: DEFINITIVE PROOF CARTRIDGE
PROPELLANT
In a firearm, the chemical composition which, when ignited by a primer, generates gas. The gas propels the projectile. Also called powder, gunpowder, smokeless powder, blackpowder.
Also Known As: Powder, Gunpowder, Smokeless Powder, Blackpowder
PROVISIONAL PROOF CARTRIDGE (HISTORICAL)
A cartridge loaded to specified pressures higher than service loads to test barrels during manufacture, but before assembly.
PULL-THROUGH
A flexible device that is pulled through the barrel of a firearm to clean the barrel.
PUMP ACTION
An action in which a moveable fore-end is manually actuated in a motion generally parallel to the barrel. This motion is transmitted to a breech bolt assembly which performs all the functions for loading and extracting cartridges. This type of action is prevalent in shotguns and is found to a lesser extent in rifles.
Also Known As: Slide Action, Trombone Action, Pump Gun
PYRAMID SIGHT
A type of front sight of triangular appearance. Also called Barleycorn Sight.
Also Known As: Barleycorn Sight
QUICK DETACHABLE SWIVEL
A two part sling swivel which has a stud that is attached to the stock or barrel and a bow portion which is mounted on a spring plunger arrangement. The plunger passes through a hole in the stud for attachment of the bow to the firearm. They are sometimes called Q.D. Swivels, and allow for quick mounting and dismounting of a sling from a firearm.
RADIAL PRESSURE GAUGE
A British term denoting a Gauge to measure cartridge-developed pressure through the sidewall of a case or shotshell tube as opposed to measuring the pressure transmitted through the head.
RAMP SIGHT
A sight blade and/or base with a rearward-facing sloped surface.
RAMROD
A rod used in seating a load in muzzle loading firearms.
RANGE
1. An area equipped for testing or using firearms and ammunition. 2. An area designated for engaging in shooting sports. 3. The horizontal distance between the firearm and the target.
RATCHET
A notched wheel on the rear of a revolver cylinder which causes the cylinder to rotate when so urged by a lever called a Hand or Pawl.
Also Known As: Hand, Pawl
RATE OF TWIST
The distance required for the rifling to complete one revolution.
REAR SIGHT
Any metallic sight used in conjunction with a metallic front sight located anywhere between the shooter eye and the front sight.
REBARREL
The replacing of a barrel with another barrel.
REBATED CARTRIDGE
A centerfire cartridge case whose rim diameter is smaller than the diameter of the body of the case at the head.
Also Known As: Rebated Case, Rebated Head
REBOUND LEVER
A rotating device designed to move the hammer into a position in which there is no contact of either hammer and firing pin or firing pin and primer. It may also be used to position a safety device between the hammer and firing pin or primer.
REBOUND SLIDE
A reciprocating device found in some double action revolvers which moves the hammer into a position in which there is no contact of either hammer and firing pin or firing pin and primer. It can also be used to position a safety device between hammer and firing pin or primer in such revolvers.
Also Known As: Rebound
REBOUNDING HAMMER
A feature of some firearms, wherein the hammer, after striking the firing pin, retracts slightly away from the firing pin before coming to rest.
REBOUNDING LOCK
A type of firing mechanism, wherein the hammer or striker after forward movement retracts slightly to a rest position.
RECEIVER
The basic unit of a firearm which houses the firing and breech mechanism and to which the barrel and stock are assembled. In revolvers, pistols, and break-open guns, it is called the Frame.
Also Known As: Frame
RECEIVER BRIDGE
That part of the receiver on bolt action rifles that arches over the rear of the bolt hole. If cut to allow the passage of the bolt handle it is known as a Split Bridge.
Also Known As: Split Bridge
RECEIVER RING
The front part of the receiver on bolt action rifles into which the barrel is fitted.
RECEIVER SIGHT
Any rear sight fitted to the receiver of a firearm, but usually refers to an aperture or “peep” sight.
Also Known As: Peep Sight, Aperture Sight
RECESSED BOLT
A bolt with a counterbore in the forward end to accommodate the head of the cartridge case.
RECHAMBER
The cutting of a new chamber in a barrel to accommodate a cartridge of the same bore diameter.
RECOIL
The rearward movement of a firearm resulting from firing a cartridge or shotshell. Sometimes informally called “Kick”.
Also Known As: Kick
RECOIL ABSORBER
Any device that reduces the perceived recoil of a firearm.
RECOIL LUG
A block or plate on the bottom of a receiver and/or barrel to transfer the recoil to the stock.
Also Known As: Recoil Shoulder
RECOIL OPERATED ACTION
A self-loading type firearm in which the force of recoil is used to unlock the breech bolt and then to complete the cycle of extracting, ejecting and reloading.
Also Known As: Recoil Operated
RECOIL PAD
A butt plate, usually of rubber, to reduce the sensible recoil of shoulder firearms.
RECOIL PENDULUM
A device for measuring Free Recoil Energy in which a firearm is suspended from fixed points so as to allow it to swing freely while the barrel remains horizontal.
RECOIL PLATE
Steel insert in the frame of a revolver immediately surrounding the firing pin hole; also called Firing Pin Bushing.
Also Known As: Firing Pin Bushing, Bolster Face
Related Terms: RECOIL LUG
RECOIL SHIELD
On a revolver, a lateral extension of the standing breech, to each side, to prevent fired or unfired cartridges from coming out of the chambers and to protect the otherwise exposed primers of unfired cartridges.
RECOIL SPRING
A spring used to store some recoil energy and subsequently close the action and feed the next round in semiautomatic firearms. In other designs, a recoil spring may serve to absorb recoil energy or perform other functions.
Also Known As: Counter Recoil Spring, Operating Spring, Closing Spring, Retracting Spring
REDUCED CHARGE
A less than nominal powder charge.
REFERENCE AMMUNITION
Ammunition used to qualify and/or calibrate velocity and pressure measuring systems.
REGULATING BARRELS
The adjusting of the relationship of the axes of multi-barreled firearms so as to make the points of impact coincide at a given distance.
RELEASE TRIGGER
An unconventional mechanism generally found only in some trap shotguns in which the firearm is fired by the release of, rather than the pull of, the trigger.
RELIEF ENGRAVING
The carving of raised scenes that produces three-dimensional figures.
RELOADING
The process of reassembling a fired cartridge case with a new primer, propellant and bullet or wads and shot. Also called Handloading when performed manually. See Handloading.
Related Terms: HANDLOADING
RELOADING COMPONENTS
Cartridge cases (new or used), primers, propellant powder, bullets, or shot and wads, used in handloading ammunition.
RELOADING DATA
A description of recommended relationships of reloading components.
RELOADING DIES
Tools which hold and/or reform cartridge cases or shotshells during a reloading operation.
RELOADING POWDER
Propellant made available to consumers for handloading ammunition. Also called Canister Powders.
Also Known As: Canister Powder
RELOADING PRESS
A mechanical device for hand-loading metallic cartridges or shotshells.
REMAINING VELOCITY
Velocity that a projectile retains at any specific location along its trajectory path.
REPEATER
Any firearm equipped with a magazine that holds more than one shot without reloading.
RESIDUAL PRESSURE
The pressure level that remains in the cartridge case or the shell within the firearm’s chamber, and in the bore, the moment the projectile leaves the muzzle of the firearm.
REST
A device to support a firearm during firing.
RESTOCK
The replacement of one stock with another.
RETICLE
The aiming reference seen when looking through a telescopic sight.
RETRACTOR
Part used to move a breech bolt to rear.
REVOLVER
A firearm, usually a handgun, with a cylinder having several chambers so arranged as to rotate around an axis and be discharged successively by the same firing mechanism through a common barrel.
RIB
A raised surface used as a sighting plane. Ribs may be either solid or ventilated. See Ventilated Rib.
Related Terms: VENTILATED RIB
RIB EXTENSION
The protrusion of a rib beyond the breech end of a barrel.
RICOCHET
The glancing rebound of a projectile after impact.
RIFLE
A firearm having helical features in the bore to impart spin to a single projectile and designed to be fired from the shoulder.
RIFLED SLUG
A projectile with helical features and a hollow base, intended for use in smoothbore shotguns.
RIFLING
Any type of helical internal bore feature of the barrel wall that imparts spin on the projectile for the purpose of stabilizing it in flight. This may be a series of lands and grooves, polygonal, hexagonal, or other configurations.
RIFLING BROACH
A tool having a series of cutting edges of progressively increasing height used to cut the helical features in a rifled barrel.
RIFLING HEAD
That part of the hook or cut rifling tooling that holds the cutter and the mechanism for deepening the cut as the operation progresses.
RIFLING PITCH
The distance the projectile must move along a rifled bore to make one revolution. Usually expressed as “one turn in x inches (or millimeters).”
Also Known As: Twist Rate
RIM
The flanged portion of the head of a rimfire cartridge, certain types of centerfire rifle and revolver cartridges and shotshells. The flanged portion is usually larger in diameter than the cartridge or shotshell body diameter and provides a projecting lip for the firearm extractor to Engauge so that the cartridge or shotshell may be extracted from the chamber after firing. In a rimfire cartridge the rim provides a cavity into which the priming mixture is charged.
RIM SEAT
A counterbore in the rear end of a chamber or bolt face to support the head of a rimmed cartridge.
RIMFIRE CARTRIDGE
A rimmed cartridge design in which the rim is formed with a cavity to contain the priming mix.
RIMFIRE PRIMER
A type of primer found in the circumferential cavity or rim of rimfire ammunition. Usable only with rimfire guns. See Centerfire Primer.
Related Terms: CENTERFIRE PRIMER
RIMLESS CASE
A centerfire cartridge whose case head is of the same diameter as the body and having a groove turned forward of the head to provide the extraction surface.
Also Known As: Rimless Cartridge
RIMMED CASE
A cartridge having a rimmed or flanged head that is larger in diameter than the body of the case. May be either rimfire or centerfire.
Also Known As: Rimmed Cartridge
RING BULGE
A circumferential bulge in a barrel typically caused by firing into an obstructed bore. See also Bulged Barrel.
Also Known As: Ringed Barrel
Related Terms: BULGED BARREL
RIVELLING
A British term for the wrinkled appearance of some shotgun bores.
ROLL CRIMP
A method of securing a bullet into a metallic cartridge case by bending the case mouth inward. See Taper Crimp.
ROLLED CRIMP
A method of closing the mouth of a shotshell by inverting the mouth of the tube upon itself over a top wad or slug. See Folded Crimp.
ROLLING BLOCK ACTION
A single shot action in which a breech block and hammer rotate about separate transverse pins in the receiver. The two members are swung rearward, away from the barrel breech to load the chamber or extract a cartridge case. To fire a cartridge, the breech block is closed and locking is accomplished by the falling hammer engaging an abutment under the breech block.
Also Known As: Rolling Block
ROTARY MAGAZINE
A form of magazine in which the cartridges are arranged about a central rotating spindle or carrier. See Mannlicher Magazine.
Also Known As: Spool Magazine
Related Terms: MANNLICHER MAGAZINE
ROUND
One complete small arms cartridge.
ROUND BALL PROJECTILE
A spherical projectile, usually of lead or lead alloy.
ROUND BUTT
A design of a handgun backstrap in which the lower portion features a rounded profile.
ROUND NOSE BULLET
An elongated projectile with a radiused nose.
RUPTURE
A generally circumferential separation in the side wall of a cartridge case. May be complete or partial.
Also Known As: Case Head Separation, Case Separation, Case Rupture
SAAMI
The acronym for the Sporting Arms and Ammunition Manufacturers’ Institute.
SABOT
(Pronounced saˈbō or ˈsabō) A carrier for firing a sub-caliber projectile in a larger bore firearm. The sabot is intended to seal the bore and center the sub-caliber projectile in the bore. In most circumstances the sabot separates from the projectile after exiting the barrel.
Also Known As: Sabot Type Projectile
SADDLE RING
A ring usually attached to the receiver of a firearm designed to be carried by a horseback rider.
SAFE
An incorrect generic term for Safety.
SAFE CARRYING CONDITION
The condition in which it is contemplated that a particular design of firearm is to be carried.
SAFETY (HANDLING)
Precautions taken by firearms users to help provide protection against accidental or unintentional discharge.
SAFETY (MECHANISM)
A device on a firearm intended to provide protection against unintended discharge under normal usage when properly engaged.
1. “On” – A term describing the position of a component of the safety device when set in a manner to provide protection against unintended discharge under normal usage.
2. “Off” – A term describing the position of a component of the safety device when set in a manner to allow the firearm to be discharged.
SCHNABEL
A German term for a hook shaped knob at the forearm tip of a stock.
Also Known As: Schnabel Fore-End
SCHUETZEN BUTTPLATE
An extremely concave metal butt plate with a rearward extension usually at the bottom used mostly on target rifles for offhand (standing) shooting.
SCOPE SIGHT
A sight containing optical elements which may or may not magnify or enlarge the target.
Also Known As: Telescopic Sight, Riflescope
SEAR
A part which retains the hammer or striker in the cocked position. When released, it permits firing.
SEASON CRACKING
A term used for stress-corrosion cracking that involves metallic cases or shotshell cups with both residual stress and specific corrosive agents.
SEATING
The positioning of a primer or bullet in a metallic cartridge case or a wad in a shotshell.
SEATING DEPTH
The longitudinal position of a bullet, primer or wad in a cartridge case.
SECANT OGIVE
A projectile nose with the curvature not tangent to the cylindrical bearing portion.
SECTIONAL DENSITY
The ratio of bullet weight to its diameter.
SEGMENTED CRIMP COLLET CRIMP
A method of securing a bullet into a metallic cartridge case by using a chuck (collet) to exert a clamping force around the mouth of the shell case.
SELECTIVE SINGLE TRIGGER
An arrangement on double-barrel firearms having a single trigger which enables the shooter to choose the barrel he wishes to fire first. The mechanism will then subsequently switch to the unfired barrel, which a second pull of the trigger can then fire.
SELECTOR
1. In a double barreled gun, a device to allow the shooter to choose which barrel is to be fired by the first pull of the trigger. 2. A lever which enables the shooter to choose the type of fire, semi-auto or full auto, with high or low rate of automatic fire.
SELF-LOADER
An action in which each pull of the trigger results in a complete firing cycle from discharge through reloading. It is necessary that the trigger be released and pulled for each firing cycle. Also called Autoloader or Self-Loader. For Blowback Operated: See Blowback Action. See Delayed Blowback Action. For Recoil Operated: See Recoil Operated Action. For Gas Operated Action: See Gas Operated Action. For Inertia Operated: See Inertia Operated Action
Also Known As: Semiautomatic
Related Terms: BLOWBACK ACTION, DELAYED BLOWBACK ACTION, GAS OPERATED ACTION, INERTIA OPERATED ACTION, RECOIL OPERATED ACTION
SEMI-FINISHED STOCK
The term for a stock which has been rough shaped and partially or completely inletted.
SEMI-INLETTED STOCK
A firearm stock that has been machine inletted and requires additional hand fitting to achieve proper fit. Also called Rough Inletted.
Also Known As: Rough Inletted Stock
SEMI-JACKETED BULLET
A bullet with a partial jacket exposing a lead nose.
SEMI-JACKETED HOLLOW POINT BULLET
A projectile having a jacket exposing a lead nose with a cavity.
SEMI-RIMMED CASE
A centerfire cartridge having a case head only slightly larger in diameter than the case body and an extractor groove just forward of the head.
Also Known As: Semi-Rimmed Cartridge
SEMI-WADCUTTER BULLET
A projectile with a distinct shoulder and short truncated cone at the forward end.
Also Known As: Semi-Wadcutter
SEMIAUTOMATIC
Firearm which fires, extracts, ejects and reloads once for each pull and release of the trigger. Also called Self-loading or Auto-loading.
Also Known As: Self-Loader, Self-Loading, Auto-Loading
SEMIAUTOMATIC ACTION
A self-loading, magazine-fed firearm in which each pull of the trigger results in a complete firing cycle from firing through loading. It is necessary that the trigger be released and pulled for each firing cycle. See
Also Known As: Semiautomatic, Auto-Loader
Related Terms: SELF-LOADER
SENSITIVITY TEST FOR PRIMED SHELLS OR PRIMERS
A method of determining the sensitivity of primed cases held in a specified die and subjected to a range of specified firing pin blows imparted by a freely falling ball. Commonly called Drop Test.
Also Known As: Drop Test, Primer Drop Test
SERIAL NUMBER
A number applied to a firearm by the manufacturer in order to identify the individual firearm.
SERRATED TRIGGER
A trigger having longitudinal grooves on its face.
SERRATION
Narrow parallel grooves cut into a surface to provide a gripping surface or to break up light reflections.
SERVICE LOAD
Commercially loaded, sporting ammunition, intended to meet the full service requirements of the targeted consumer.
Also Known As: Service Cartridge
SERVICE LOADS
1. Commercially available sporting ammunition. (As opposed to proof, reference, etc., or other special use ammunition). 2. Ammunition carried by Police Officers on duty. Also, ammunition carried by soldiers in combat, as opposed to special service ammunition, i.e. Match, Armor-piercing, etc.
Also Known As: Ammunition Service
SET TRIGGER
Either a single or double trigger arrangement on which the required trigger pull force can be made very light by means of “setting” mechanism. May be either Double Set trigger or Single Set trigger.
SETTING
The arming of a set-trigger mechanism of a firearm so equipped. See Set Trigger.
Related Terms: SET TRIGGER
SHEATH TRIGGER
A trigger which has a minimum projection from the action and is not usually surrounded by a trigger guard. Also called Spur Trigger.
Also Known As: Spur Trigger
SHELL
Generic term for the unloaded case for metallic or shotshell ammunition. A colloquial term incorrectly used for loaded ammunition.
SHELL CATCHER
A device for catching fired shells.
SHELL HOLDER
A device for holding the head of a cartridge case in a reloading tool.
SHOCK WAVE
The disturbance of air surrounding and behind the bullet caused by a compression of the air column directly in front of the bullet.
SHOCKING POWER
A colloquial term used to describe the ability of a projectile to dissipate its kinetic energy effectively in a target.
SHOE
1. A metallic adapter fastened to a trigger to widen the surface. 2. A metallic insert in the forearm of a side-by-side double barreled shotgun by which the forearm is attached to the barrels. Also called Fore-end Iron, Fore-end Plate.
Also Known As: Fore-End Iron, Fore-End Plate
SHOOT-OFF
The separation of the mouth end of a shotshell from the body when it is fired.
SHOOTING GLASSES
Eye protection and sight improvement specifically designed for, and which should always be used, when shooting firearms.
SHORT
A type of 22 caliber rimfire cartridge.
SHORT ROUND
A cartridge in which the bullet is seated below the specified minimum length.
SHOT
Spherical pellets used in loading shotshells. Commonly formed from lead but may be made from steel or other material.
SHOT BRIDGING
A wedging action of shot pellets in a tube causing a stoppage of flow in a shotshell loading operation.
SHOT CARTRIDGE
A centerfire or rimfire cartridge loaded with small diameter shot.
SHOT COLUMN
The length of the shot load in a shotshell.
SHOT DIVERTER
A device attached to the muzzle of a shotgun to provide oval shot patterns.
SHOT SIZE
A numerical or letter(s) designation indicating the average diameter of a pellet. With numerical designations, the average pellet diameter may be determined as follows: Shot Size = (17 – Number Designation)/100 For example, for No. 6 shot: (17-6)/100 = 0.11” 17 – Designation Number = Avg. Shot diameter in hundredths of an inch 100 EXAMPLE: For No. 10 Shot: 17-10 = 7/100 = .07”
SHOT STRING
The distance between the leading and trailing pellets of a shot charge in flight.
SHOT TOWER
A tall building in which molten lead alloy is dropped through a colander near the top of the tower into a tank of water at the bottom to produce spherical pellets.
SHOT-COLLAR
A plastic or paper insert surrounding the shot charge in a shotshell to reduce distortion of the shot when passing through the barrel.
SHOT-PROTECTOR WAD
Various designs of shot cups made of plastic and designed to reduce pellet deformation during barrel travel.
Also Known As: Shot Cup
SHOTGUN
A smooth bore firearm designed to fire cartridges containing numerous pellets or a single slug and designed to be fired from the shoulder. In some cases, shotgun bores or choke tubes are rifled to be used specifically with slugs.
SHOTGUN STOCK
Any stock used on a shotgun. See Two Piece Stock.
Related Terms: TWO PIECE STOCK
SHOTSHELL
A round of ammunition containing multiple pellets for use in a shotgun.
SHOULDER
1. Act of placing a shotgun or rifle to a shooter’s shoulder, in order to properly align the sights and fire at a target. 2. The sloping portion of a metallic cartridge case that connects the neck and the body of a bottleneck-type cartridge. 3. The square or angular step between two diameters on a barrel, pin, stud or other part commonly used in sporting firearms.
SHOULDER RADIUS
The curved surface between the body and the shoulder of a cartridge case.
SHOULDER SPLIT
A longitudinal rupture in side wall of the shoulder of a bottlenecked cartridge case.
SHOULDER-ARM
Any firearm fitted with a stock and designed to be used while held with both hands and supported by a shoulder.
Also Known As: Long Gun
SIDE LOCK ACTION
An action in which the fire control system is attached to a side plate rather than being integral with the frame or trigger plate.
Also Known As: Action Bar Lock
SIDE PIN OR SCREW
Screw used to attach side-locks to frame and/or stock.
SIDE-BY-SIDE
A firearm with two barrels arranged adjacently in the horizontal plane.
SIDE-HAMMER
A firearm with the hammer located externally on the side of the frame as contrasted to an internally pivoted hammer.
SIDE-LOCK
A form of firearm construction that has the firing mechanism mounted on detachable plates on the side.
SIDE-PLATE
A removable plate in the frame or receiver to allow access to internal parts or upon which some internal parts are mounted.
SIDEARM
A handgun (pistol or revolver).
SIGHT
Any of a variety of devices, mechanical or optical, designed to assist in aiming a firearm.
SIGHT ADJUSTMENT
The movement of a sight to change the point of impact.
SIGHT APERTURE
The hole in the disc of an Aperture Sight. Aperture Sight
Related Terms: APERTURE SIGHT
SIGHT BASE
That part of a sight that is usually attached to a gun.
SIGHT BEAD
The small cylindrical top portion on some forms of front sights.
SIGHT BLADE
1. (Front sight) An elongated projection usually mounted parallel to the bore, used as the front sight on some firearms. See Blade Sight. 2. (Rear sight) An elongated movable portion of an adjustable rear sight that incorporates the sighting notch or aperture.
Related Terms: BLADE SIGHT
SIGHT COVER
Protective metal cover fastened about a sight to guard it from being moved out of adjustment from jars or blows. Sometimes called a Sight Hood or Hooded Sight.
Also Known As: Sight Hood, Hooded Sight
SIGHT DISC
That part of an aperture (peep) sight that contains the hole. May have either a fixed orifice or contain an iris diaphragm to vary its size.
SIGHT ELEVATION
The height to which a rear sight is set to zero-in the firearm for any specific range.
SIGHT EXTENSION
A device that increases the distance between the sights.
SIGHT INSERTS
Metal or plastic discs with either apertures or posts for use in globe front sights.
SIGHT LEAF
The vertical portion of a metallic rear sight containing the notch.
SIGHT PICTURE
The visual image observed by the shooter when the firearm sights are properly aligned on the point-of-aim.
Also Known As: Sight Alignment
SIGHT RADIUS
The distance between the rear sight and the front sight on a firearm.
SIGHT RAMP
A sight base having a sloping rear surface on which a front or rear sight may be mounted.
SIGHTING-IN
The procedure of adjusting the sights so as to bring the point of impact to coincide with the point of aim.
Also Known As: Zero-In
SIGHTING-SHOT
Shot(s) fired to determine point of impact.
SINGLE ACTION
A firing mechanism in which the trigger serves the sole purpose of releasing the firing mechanism – either hammer or striker. For differentiation: See Double Action. See Double Action Only.
Related Terms: DOUBLE ACTION, DOUBLE ACTION ONLY
SINGLE ACTION PISTOL
A pistol mechanism which requires the manual cocking of the hammer or striker before pressure on the trigger releases the firing mechanism.
SINGLE ACTION REVOLVER
A type of revolver in which the hammer must be cocked manually to rotate the cylinder for each shot. The firearm is then discharged by a pull of the trigger. The process is repeated for each shot.
SINGLE BASE POWDER
Smokeless propellant powder which has colloided nitrocellulose as its main ingredient, and contains no other major energy-producing component. The nitrogen content of the nitrocellulose is usually between 13.1% and 13.2%. In the United States, single base powders contain no nitroglycerine, whereas in some European countries powders containing less than 10% nitroglycerine are considered single base. See Double Base Powder for comparison.
Also Known As: Nitrocellulose Powder
Related Terms: DOUBLE BASE POWDER
SINGLE POINT SLING
A strap design that attaches to only one point on the firearm.
SINGLE SHOT
A firearm with no means in the mechanism for storing or loading more than a single cartridge housed in the chamber of the barrel.
SINGLE SHOT ACTION
An action that will only accept a single cartridge that must be manually loaded into the firearm’s chamber each time it is fired.
Also Known As: Single Shot
SINGLE STAGE TRIGGER
1. A trigger mechanism in which the trigger travel is relatively short and there is no significant sensible change in pull force from the beginning of movement up to the point of firing. 2. A trigger which releases with a single pull.
SINGLE TRIGGER
A trigger mechanism for multiple barrel firearms wherein repeated pulls of one trigger fires the barrels successively.
SINGLE-DOUBLE TRIGGER
A type of trigger mechanism found on some double-barrel or over-under shotguns consisting of two triggers. The front trigger functions as a conventional non-selective single trigger, while the rear trigger will fire only the barrel with the tighter choke.
SIX O'CLOCK HOLD
A sight picture where the top of the sight is tangent to the bottom of the bullseye.
SIZING
1. The reduction in diameter of a bullet by forcing it through a die of smaller diameter than the bullet. 2. The reduction in diameter of a cartridge case by forcing it into a die of smaller diameter than the case.
Also Known As: Bullet Sizing, Cartridge Case Sizing
SIZING DIE
A tool used to form a cartridge case or bullet to proper dimensions.
SKEET GUN
A shotgun with a choke of minimal constriction specifically designed for Skeet shooting or may also be used for close range game hunting.
SKEET SHOOTING
A shotgun target sport in which shooters move around a semi-circle and fire at clay targets thrown at specified angles and from a high and a low “house”, each containing a target trap.
SKELETON BUTT PLATE
A metal buttplate forming only a border for the butt.
SKID MARKS
Longitudinal rifling marks formed on the bearing surface of bullets as they enter the rifling of the barrel before rotation of the bullet starts.
Also Known As: Rifling Marks
SKIP-LINE CHECKERING
A type of gunstock line engraving where lines are omitted at regular intervals. Also called Skip-a-line, or Skip-Line, or French checkering
Also Known As: French Checkering, Skip-a-Line, Skip-Line
SLAVE ACTION
A special substitute action used for testing a barrel or barrels.
SLAVE PIN
A pin used during assembly of a firearm to facilitate the process and later replaced by a permanent pin or screw.
SLEEVE
1. A means of renewing old shotgun barrels by insertion of a tube into the bore or interior of the barrel. 2. A tube surrounding the receiver of a target rifle to improve rigidity. 3. The shot container in a shotshell. 4. The inner, rifled portion of a two-piece barrel.
Also Known As: Barrel Sleeve
SLIDE
A member attached to and reciprocating with the breech block.
Also Known As: Pistol Slide
SLIDE LOCK, ACTION BAR LOCK
The part of a mechanism, normally found on slide action firearms that locks the forearm/slide mechanism in the forward position.
SLIDE STOP
Device to retain slide in an open position.
SLIDING SAFETY
A manual safety mechanism on a firearm that is operated by a longitudinal sliding motion.
Also Known As: Tang Safety
SLING
A strap detachably fastened to a firearm to assist in carrying or to steady it during firing.
Also Known As: Rifle Sling, Strap
SLOT BLANK
A dovetail-shaped metal part to occupy an unused dovetail slot.
SLOTTED TIP
A cleaning rod tip with a slot to hold a cleaning patch.
SLUG
A single projectile fired from a shotgun. Also slang term for bullet after it has been fired from a firearm.
SLUGGING (BORE)
A process of determining the interior dimensions of a barrel or cylinder by measuring a deformable material which has been pressed through the bore.
Also Known As: Bore Slugging
SMALL ARMS
A term that has numerous definitions (military, political, regulatory etc.). For the purpose of firearms that fall under SAAMI: See Sporting Arms.
SMALL BORE CARTRIDGE
General term applied in the United States to 17 and 22 caliber rimfire cartridges. Normally used for target shooting and small game hunting.
SMALL OF THE STOCK
That portion of the stock between the rear of the action and the comb, which has the smallest circumference.
Also Known As: Wrist
SMALL-BORE
In America, any firearm or ammunition of the rimfire type with a lead alloy bullet not over 0.23” in diameter.
SMOKELESS POWDER
A propellant containing mainly nitrocellulose (single base) or both nitrocellulose and nitroglycerine (double base).
SMOOTH-BORE
Firearm with unrifled bore, typically a shotgun.
SNAP-CAP
A protective device to permit dry firing without damage to the firing pin.
SOFT POINT PROJECTILE
A design providing for exposure of a portion of the core at the nose of a jacketed bullet, to initiate expansion of the projectile upon impact.
Also Known As: Soft Point Bullet
SOLID FRAME
1. In shoulder arms, a firearm in which the barrel and receiver are not designed for quick disassembly. 2. In handguns, having a frame that is not hinged.
SOLID RIB
A solid raised surface above a barrel or barrels which functions as a sighting plane.
SPEED OF ROTATION (SPIN)
The rate of spin of a projectile fired from a rifled barrel.
SPENT PROJECTILE
A bullet which has lost all of its kinetic energy.
Also Known As: Spent Bullet, Spent Slug
SPHERICAL PROPELLANT
Smokeless Propellant manufactured by a process in which nitrocellulose is first lacquered with solvents then being processed into a sphere. The finished product may take the form of a sphere, flattened sphere, or cylinder.
SPIN DRIFT
The deviation from the expected flight path of a bullet due to the gyrational spin of bullet imparted by the rifling.
SPIRE POINT PROJECTILE
A pointed projectile characterized by a sharply secant ogive or a conical nose profile.
Also Known As: Spire Point Bullet
SPITZER PROJECTILE
A pointed projectile characterized by a long tangent or slightly secant ogive.
Also Known As: Spitzer Bullet
SPLIT BASE
A longitudinal split in the sidewall of the brass or steel cup assembled on a plastic or paper shotshell.
Also Known As: Cup Split
SPLIT NECK
A longitudinal rupture in the neck of a metallic cartridge case.
Also Known As: Neck Crack
SPLIT RIM (RIM-SPLIT)
A circumferential rupture of the rim of a rimfire cartridge or shotshell.
SPORTERIZE
The act or process of converting a military weapon to a sporting firearm, usually by removing unneeded accessories, and altering the barrel and/or stock.
SPORTING ARMS
Sporting arms are generally considered rifles and handguns up to and including 50 caliber and shotguns up to and including 10 gauge, with some limited exceptions pertaining to caliber, gauge, or type.
SPORTING ARMS AMMUNITION
Ammunition for Sporting Arms. See Sporting Arms.
Related Terms: SPORTING ARMS
SPREADER LOAD
A shotshell load specifically designed to provide a widely spread pattern at a close range. Also called Scatterload, Bush Load, Thicket Load.
Also Known As: Brush Load, Thicket Load, Bush Load, Scatterload
SQUARE BUTT
Handle of a revolver with a flat or squared end.
SQUIB LOAD
A cartridge or shell which produces projectile velocity and sound substantially lower than normal. May result in projectile and/or wads remaining in the bore.
Also Known As: Squib
STAB CRIMP
A method of securing a bullet or primer into a metallic cartridge case by means of multiple indentations.
STAKE CRIMP
A method of securing a primer into a metallic cartridge case by deforming the primer pocket mouth inward.
STANDARD VELOCITY
An industry term for rimfire ammunition loaded to a velocity level below high velocity ammunition of that type.
STANDING BREECH
The fixed vertical face of a frame, typical of a break-open firearm, which contains the striker(s) or firing pin(s).
STAR CRIMP
A type of closure of the mouth of a metallic case or shotshell in which the sidewalls are folded in a star-shaped pattern.
Also Known As: Rose Crimp, Pie Crimp
STAR GAUGE
A measuring instrument for determining internal diameters, often used to measure the inside diameter of a gun barrel.
STEADY-PIN
A projection at the end of a mainspring which fits into the lock plate of a side lock action gun.
STEEL JACKETED BULLET
Plated or clad steel is sometimes used as a substitute for gilding metal or copper in bullet jacket material.
STEEL SHOT
Soft steel pellets made specifically for use in shotshells.
STEM (STEMMING)
A failure of a cartridge to feed in which the bullet jams against the top or bottom of the chamber. Also called Cock-Up or Cock-Down.
Also Known As: Cock-Up, Cock-Down
STIPPLING
The roughing of wood or metal with a pointed tool. It is normally performed to provide a gripping or decorative surface. Also called Matting.
Also Known As: Matting
STIRRUP
A component with divided legs to apply force equally. Mainly used in a trigger assembly where it is necessary to straddle another component.
STOCK
The wood or plastic component to which the metal parts of a firearm are attached to enable the shooter to hold the firearm.
STOCK BOLT
A bolt which passes through a buttstock lengthwise to secure it to the receiver or frame.
STOCK DIMENSIONS
General stock dimensions consist of the following: length of pull, drop at comb, drop at Monte Carlo, drop at heel, pitch and cast.
A. Rifles 1. Cast is the lateral displacement of the centerline of the buttplate (pad) from the centerline of the bore. For a right-handed shooter, when the centerline of the buttplate is to the left of the bore, it is expressed as cast-on and to the right as cast-off. The opposite is true for left-handed shooters. 2. Drop is the vertical distance from the line of sight to the comb, Monte Carlo or heel of the stock. It is measured from an extension of a straight line drawn from the top of the front sight through the top surface of the open rear sight adjacent to the notch. The drops for target rifles are usually measured from the centerline of the bore. 3. Girth – The smallest circumferential dimension at the pistol grip. 4. Length of Pull – The distance from the center of the trigger to the center of the buttplate or recoil pad. 5. Length of Stock – The greatest dimension of the stock material. 6. Pitch – Not usually given for rifle.
B. Shotguns 1. Cast – Same as A.1., above. 2. Drop is the vertical distance from the line of sight to the comb, Monte Carlo or heel of the stock. It is measured from an extension of a straight line drawn from the base of the front bead sight across the highest point on the frame or receiver. 3. Girth – Same as A.3., above. 4. Length of Pull – same as A.4., above. 5. Length of Stock – Same as A.5., above. 6. Pitch is an expression used to indicate the relationship of the bore to the plane of the buttplate (pad). It is found by extending a line across the butt and drawing at right angles to this line an additional line through the highest point on the receiver or frame and measuring the distance from an extension of this line to a point at the base of the front sight bead. The pitch is said to be if the described line is above the front sight and if below. The pitch is normally down.
Also Known As: Drop at Comb, Drop at Heel, Drop at Monte Carlo, Cast
STOCK PITCH
The angle at which the buttplate or recoil pad slopes in relation to the bore axis. For method of measuring, see Stock Dimensions.
STOCK SCREW
A screw used for attaching the stock to the receiver or frame of a firearm. More than one may be used per firearm.
STOCK WARPAGE
The twisting and bending of a wood stock due to moisture absorption.
STOCKMAKER'S HAND SCREWS
Extra long screws used by stockmakers during the inletting operation to maintain alignment of the trigger guard and other auxiliary items with the action. Also known as Inletting Screws or Guide Screws.
Also Known As: Inletting Screws, Guide Screws
STOPPAGE
This term is used when a firearm stops firing due to a malfunction of either the gun mechanism or ammunition. This term is normally used in connection with automatic firearms, machine guns, etc.
STOVE-PIPING
A failure to eject where the fired case is caught in the ejection port by the forward motion of the bolt The case protruding upward out of the ejection port is said to resemble an old fashioned stove pipe.
STRAIGHT GRIP
On shoulder firearms, describes a butt stock without a pistol grip.
Also Known As: English Stock
STRAIGHT PULL
A bolt action firearm in which the bolt need not be rotated to open or close the action but is reciprocated by a straight backward and forward motion of the shooter’s hand.
STRAIGHT STOCK
1. A stock with no pistol grip also known as an English Stock. 2. A “Cast-Neutral” Stock.
Also Known As: English Stock, Straight Grip Stock
Related Terms: CAST-NEUTRAL, STOCK DIMENSIONS
STRAIN GAUGE
An electronic device to measure stress and strain in mechanical devices.
STRAIN SCREW
A screw which bears against a leaf spring and by its movement in or out will change the tension of the spring.
STRIKER
A spring-driven rod-like firing pin, or a separate component which impacts the firing pin, which travels in a linear path to strike the primer.
STRIKING VELOCITY
The velocity of a projectile at the point of impact.
Related Terms: TERMINAL VELOCITY
STRIP
To disassemble a firearm in order to clean, repair or transport it. “Field stripping” is simple disassembling for cleaning; “detail stripping” is a complete disassembly of the firearm into it’s components.
STRIPPED ACTION
A receiver or frame of a firearm from which all parts have been removed.
STRIPPING
1. The act of disassembling a firearm. 2. The act of transferring cartridges from a loading (“stripper”) clip to the magazine. 3. Failure of a bullet to engage the rifling properly.
Related Terms: TAKE DOWN
STUD TRIGGER
A button-type trigger, the end of which is pressed to fire the firearm.
SUB-CALIBER AMMUNITION
A cartridge having a projectile smaller than is standard for the firearm in which it is used.
SUBCALIBER
An adaptation to a firearm to enable the firing of smaller or lower powered ammunition for which it was originally intended.
SUBCALIBER TUBE
A tube which is place in the bore of a firearm to enable the firing of smaller or lower powered ammunition.
Also Known As: Barrel Insert
SUIGI FINISH
A wood finish which is achieved by scorching to give a darkened and grainy appearance.
SUMMIT VELOCITY
The velocity of a projectile at the highest point of the trajectory.
SUPPRESSOR
A device attached to a firearm intended to reduce the sound signature of discharge.
Also Known As: Silencer, Sound Suppressor, Sound Moderator
Related Terms: INTEGRALLY-SUPPRESSED BARREL
SWAGED BULLET
A bullet that has been completely formed by impacting the bullet material into a die.
SWAGED CHOKE
A shotgun barrel constriction which has been formed at or near the muzzle by the use of dies or hammers.
SWIVEL BOW
That part of a swivel which is in the form of an elongated loop and to which a sling or carrying strap is passed through or otherwise attached.
SWIVEL SLING
A metallic loop to which the sling is attached.
Also Known As: Sling Swivel
T-BOLT
A patented reciprocation and locking system for use on a rimfire rifle. Sometimes used to describe straight-pull bolt action rifles with a horizontally protruding straight bolt handle.
TACTICAL SHOTGUN
A shotgun with a short barrel designed for tactical applications.
TAKE DOWN
To disassemble a firearm for cleaning, repair or transportation.
Also Known As: Stripping
TAKEDOWN
A type of firearm designed for ease of disassembly and transportation.
TANG
A rearward projecting tongue on a receiver or frame to which the buttstock is attached. Some parts of the operating mechanism of a firearm may also pass through the tang. A gun may have either or both an upper and lower tang.
TANG SAFETY
A type of safety in which the external control component is mounted on the upper receiver tang of a firearm.
Also Known As: Sliding Safety
TANG SCREW
The screw or screws passing through either one or both tangs by which the stock or trigger guard is attached to the receiver or frame.
TANG SIGHT
Any sight mounted on the upper tang of a firearm.
TANGENT OGIVE
A projectile nose with the curvature tangent to the cylindrical bearing portion.
TANGENT SIGHT
A rear sight in which the blade is adjusted for elevation correction by sliding along a curved cam or cams.
TAPER CRIMP
A method of securing a bullet by lightly swaging the metallic casemouth into the bullet body.
Also Known As: Taper Crimp
TARAGE TABLE
A tabulation of values relating to the compressed length of a crusher cylinder to the chamber pressure.
TARGET HAMMER
A firearm hammer having a wider spur designed for convenient and rapid cocking.
TARGET RIFLE
Any rifle designed and equipped for match or target shooting.
TARGET SHOOTING
The act of shooting at inanimate objects. “formal” target shooting is done at specified distances at targets designated for scoring. “Informal” target shooting is done at varying distances at impromptu targets for practice. See Plinking.
Related Terms: PLINKING
TARGET SIGHT
Sights designed for use in competitive shooting.
TARGET SLING
A special form of strap designed to aid in support of the firearm in target shooting.
TARGET STOCK
Any stock specifically made for firearms designed for target shooting.
TARGET TRIGGER
1. A trigger mechanism which provides for adjustment of such characteristics as pull force, travel or overtravel. 2. A trigger which provides a large bearing surface for the trigger finger. 3. A relatively light, crisp trigger designed to assist in accurate shooting.
TARGET(ING)
The act of shooting a firearm to align sights. See Sighting In.
Also Known As: Sighting In
Related Terms: SIGHTING-IN
TELESCOPE MOUNT
A device to hold a telescope on a firearm.
TELESCOPIC SIGHT
A sight containing optical elements which magnifies the target.
Also Known As: Scope, Riflescope, Telescope
TEMPERATURE OF IGNITION
The lowest temperature to which the surface of material must be raised for the combustion of the material to become self-sustaining.
TENON
1. On firearms, it is the projecting part of wood components which fit into the receiver or frame. 2. On ammunition, that portion of the rimfire bullet which fits into the cartridge case, from bullet base to bottom of band. Also called Heel. See Heel.
Also Known As: Heel
Related Terms: HEEL
TERMINAL BALLISTICS
The branch of ballistics related to the effects of projectiles at or inside the target.
TERMINAL ENERGY
The remaining energy of a projectile at the point of impact.
Also Known As: Striking Energy
TERMINAL VELOCITY
The remaining velocity of a projectile at the point of impact. See Striking Velocity.
Related Terms: STRIKING VELOCITY
TEST BARREL
A barrel of special dimensions used for testing ammunition.
THREE-QUARTER STOCK
A rifle stock which has an abnormally long fore-end, but which does not reach the muzzle.
THROAT
The tapered portion of the bore of a barrel, immediately ahead of the chamber which is sized to provide clearance for the bullet of the loaded cartridge. Also referred to as Leade or Ball Seat and is associated with Free Bore. See Free Bore.
Also Known As: Leade, Ball Seat
Related Terms: CHAMBER LEADE, FREE BORE, BALL SEAT
THUMB PIECE (CYLINDER RELEASE)
A latch used on some revolvers to release the cylinder. Sometimes called a “Thumb Latch”.
Also Known As: Thumb Latch
THUMB REST
A ledge in the grip area of a rifle or handgun on which to rest the thumb of the trigger hand.
THUMB SAFETY
A type of manual safety in which the external control component is located for convenient operation by the thumb of the trigger hand.
THUMBHOLE STOCK
Any stock having a contoured hole in the grip area to accommodate the thumb of the trigger hand.
TIME OF FLIGHT
The total elapsed time that a projectile requires to travel a specific distance from the muzzle.
TOE
The bottom (lower) end of a buttplate and adjacent portion of the stock on a shoulder firearm.
TONG TOOL
An unmounted, portable handloading tool using a plier action for handloading centerfire cartridges. Also called Nutcracker Tool.
Also Known As: Nutcracker Tool
TOP EXTENSION
A projection which extends behind the breech end of the barrels on some breakopen firearms. When the gun is closed, it fits into a corresponding recess slot in the frame and is used for locking purposes.
TOP STRAP
That portion of a revolver frame which passes over the cylinder.
Also Known As: Strap
TOP WAD
The closure disc over the top of the shot column held in place by a rolled crimp.
TOP-BREAK ACTION
An action in which the barrel or barrels are connected to the frame by a pivot point. Upon release of the locking mechanism, usually by a top, side or under-lever, the barrel or barrels rotate around the pivot point away from the standing breech.
Also Known As: Top-Break, Break-Open Action, Tip-Up,
Related Terms: STANDING BREECH
TRAJECTORY
The curved path of a projectile from muzzle to target.
Also Known As: Ballistic Curve
TRAJECTORY TABLE
A computed table describing the downrange trajectory of a projectile or of shotshell pellets, buckshot or rifled slugs.
TRAP
A clay target throwing device.
TRAP DOOR ACTION
An action in which a top-hinged breech block pivots up and forward to open. Locking on this action is accomplished by a cam piece located at the rear of the breech block that fits into a mating recess. Also known as a “Cam Lock.”
Also Known As: Cam Lock
TRAP GUN
A shotgun specifically designed for the game of Trap shooting.
TRAP SHOOTING
A shotgun target sport in which clay targets are thrown away from the shooters by a reciprocating trap located forward of the firing line.
TRAP-DOOR BUTTPLATE
A type of buttplate with a hinged closure plate in the butt-end of a firearm. Opening of the trap door exposes a recess in the stock which can be used for storage.
TRIGGER
That part of a firearm mechanism which is moved manually to cause the firearm to discharge.
TRIGGER BAR
A connecting piece between the trigger and the sear.
TRIGGER CREEP
The sensible movement of the trigger or take-up or pretravel, prior to sear release.
Also Known As: Creep
TRIGGER GUARD
A rigid loop which partially surrounds the trigger to reduce the possibility of accidental discharge.
TRIGGER LOCK
1. An accessory for blocking unauthorized trigger movement during gun storage. Must never be applied to a loaded firearm. 2. A form of firearm safety blocking trigger movement.
TRIGGER MECHANISM
Those parts which, when pressure is applied to the trigger, release the hammer or striker. Also called Fire Control.
Also Known As: Fire Control
TRIGGER PLATE (ASSEMBLY)
1. A metal plate fitted to the lower part of some frames through which the trigger or triggers pass. 2. A component attached to the frame or receiver of some firearms, which supports the major components of the firing mechanism and may have the trigger guard as an integral portion.
TRIGGER PULL FORCE
The peak force which must be applied to the trigger of a firearm, approximately parallel to the bore line, to cause the sear, striker, or hammer to release.
TRIGGER PULL SCALE
A device for measuring trigger release force.
TRIGGER SHOE
An accessory which is attached to the trigger to give a much larger trigger-finger bearing surface.
TRIGGER SQUEEZE
A gradual increase of pressure on a trigger until it releases.
TRIGGER STOP
1. A device to prevent certain firearms from being fired until the finger lever is closed. 2. A device to prevent over-travel of the trigger.
TRIP
A part of the mechanism of some firearms which is released by the action of the trigger.
TRIPLE BASE POWDER
A propellant composed of colloided nitrocellulose, nitroglycerine and nitroguanidine. Generally used in large caliber military ammunition.
TRUNCATED BULLET
A design of a flat-nosed bullet having a conical shape rather than a nose formed by a radius.
Also Known As: Truncated Projectile
TRUNCATED CONE BULLET
A design of a flat-nosed bullet having a conical shape rather than ogive formed by a curve or radius.
TRY-GUN
A shoulder firearm having a stock which is fully adjustable for length of pull; drop at comb, Monte Carlo and heel; pitch and cast. It is used for fitting of custom made firearms to a specific shooter’s physical characteristics.
TUBE
1. The cylindrical body of a shotshell. 2. Improper term for a shotgun barrel. 3. A barrel insert to allow firing of a smaller gauge shotshell.
TUBE CUTOFF
A circumferential separation of a shotshell tube or body.
TUBE SIGHT
A metal tube that contains the rear sight.
TUBULAR MAGAZINE
A metal tube that contains cartridges or shells end to end.
TUMBLER
An English term that is sometimes used to denote a shotgun hammer. Also refers to an interior part of gun locks which contain notches that interact with the sear.
TUMBLING
1. The end-over-end rotation of an unstable projectile in flight. 2. A cleaning and polishing process, sometimes used in firearm part and ammunition manufacturing.
TUNNEL MOUNT
A telescope mount arrangement which has a hollowed-out base through which the iron sights may be seen and used.
TURNBOLT ACTION
A bolt action firearm on which it is necessary to rotate the bolt handle upwards for unlocking before it can be pulled to the rear. Similarly, it is necessary to rotate the bolt handle downward after closing to lock the firearm and enable the gun to be fired.
Also Known As: Turn-Bolt
TWIN-SINGLE TRIGGER
A double trigger arrangement used on some double-barrel firearms, wherein one or both triggers will, with each pull, fire the barrels sequentially. They are non-selective.
TWIST
The distance required for one complete turn of rifling usually expressed as a ratio, e.g., 1 in 10 inches.
TWO PIECE STOCK
A stock consisting of two separate parts, the buttstock and forearm.
TWO-PIECE MOUNT
A telescope mount having two separate base band ring assemblies.
U-NOTCH SIGHT
A rear sight on pistols or revolvers having a flat top with a “U” shaped notch used with bead-topped front sight. Named after Ira Paine, 19th Century match and exhibition shooter. Also known as Paine Sight.
Also Known As: Paine Sight
UNDER-LEVER ACTION
The same as a top break mechanism except that the lever that unlocks the firearm, allowing the barrels to pivot and expose the breech, is located below the trigger guard or forms the trigger guard.
UNDERBOLT
The moveable lock of some break-open firearms. It normally engages the barrel lug (underlug) and is actuated by the top lever.
UNDERLUGS
The downward projecting lugs at the breech end of a break-open firearm used for locking and barrel positioning in the frame. Also called Lumps.
Also Known As: Lumps
UNIVERSAL RECEIVER
A heavy duty mechanical device into which chambered barrels are secured for testing ammunition.
UNLOAD
1. The complete removal of all ammunition from a firearm and it’s magazine 2. Disassembly of a cartridge or shell.
UNSERVICEABLE
A firearm which, for any reason, is no longer fit for firing.
UPSET FORGING
A gun barrel blank formed by hammering a steel bar to increase its diameter at one end for the purpose of providing a shank section.
VARIABLE CHOKE
An adjustable device attached to the muzzle of a shotgun in order to control the shot patterns.
VARMINT RIFLE
A sporting rifle with a heavy barrel, designed for long range small game hunting, firing high velocity, flat trajectory projectiles.
VELOCITY
The speed of a projectile at a given point along its trajectory.
VENTILATED CHOKE
A shotgun choke which is perforated for the release of propellant gases.
Also Known As: Choke, Ported
VENTILATED RIB
A raised sighting surface which is separated from the barrel by means of posts that allow air to circulate around it. Its purpose is to minimize heat waves in the line of sight. Also called Bridge Rib.
Also Known As: Bridge Rib
VERNIER SIGHT
A long-range sight with a mechanism for adjusting windage and/or elevation settings as read on a short scale in conjunction with graduations on a longer, linearly calibrated, scale.
VERTICAL DISPERSION
The greatest vertical distance between any two bullet holes on a target, normally measured center-to-center.
WAD COLUMN
The wads between propellant and shot pellets in a specific shotshell.
WAD CUTTER
A device for cutting wads from sheet stock.
WAD PRESSURE
The force applied to a wad column as it is seated firmly against the propellant.
WADCUTTER BULLET
A generally cylindrical bullet design having a sharp shouldered nose intended to cut target paper cleanly to facilitate easy and accurate scoring.
Also Known As: Wadcutter
WALKING BARREL
A gun barrel which changes its center-of-impact point when heated by firing.
WARMING SHOTS
Preliminary shots before firing for velocity, pressure, accuracy, etc.
WATER TABLE
The flat portion of the frame on break-open firearms which extends forward from and is approximately at right angles to the standing breech face. It is the surface on which the barrel flats rest when the gun is closed.
WAX BULLET
A bullet made from paraffin and other wax preparation, usually for short range indoor target shooting.
WEAPON
An instrument used in anti-personnel combat. The term is never used when referring to target or sporting firearms.
WEB
1. The solid portion of a brass centerfire cartridge case between the inside of the case at the head and the bottom of the primer pocket. 2. The smallest dimension of a smokeless powder kernel.
WHELEN STOCK
A rifle stock developed by Colonel Townsend Whelen which features a forward sloping comb and cheekpiece.
WILDCAT CARTRIDGE
A “Wildcat Cartridge” is a cartridge for which the dimensions, performance and pressure levels standards have not been standardized by a recognized standards-setting organization such as SAAMI, the C.I.P., NATO or other governmental body.
WIND DRIFT
The deviation from the expected flight path of a bullet due to the forces of wind.
WINDAGE ADJUSTMENT
The transverse movement of a sight to compensate for the horizontal displacement of a bullet or bullets from the aiming point.
WINDAGE KNOB
The knob on some iron and telescopic sights which is turned in either direction to adjust the horizontal setting of the notch, aperture or reticle of the sight.
WINDAGE MICROMETER
A micrometer type device found on some iron and telescopic sights which allows the shooter to make precision adjustments to the horizontal setting.
WING SAFETY
A manual safety found on some bolt action rifles, usually mounted at the rear of the bolt assembly, which pivots in an arc at right angles to the bore line.
Also Known As: Pivot Safety
WITNESS MARK
A line on each of two mating parts used to indicate proper alignment. Also known as Draw-Line or Index Mark.
Also Known As: Draw-Line, Index Mark
WUNDHAMMER SWELL (BULGE)
A bulge or swelling in the pistol grip of a stock to fit the palm of the trigger hand. Named after inventor Louis Wundhammer.
X-RING
A circle inside the highest scoring ring on a target, used to break ties in shooting matches. The shooter with the most X-Ring hits wins.
YAW
The angle between the longitudinal axis of a projectile and a line tangent to the trajectory through the center of gravity.