Glossary

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 definition 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.

Terms made up of two or more words are defined under the principle word: e.g., a “Frangible Bullet” is defined under “Bullet, Frangible” or a “Free Rifle Stock” is defined under “Stock, Free Rifle.”

A

ABSORBER, RECOIL

Any device that reduces the perceived recoil of a firearm.


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.


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

Common term used in conjunction with firearms which have been subjected to special fitting and operations in the interest of improved accuracy.


ACTION

The combination of the receiver or frame and breech bolt 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.


ACTION BAR LOCK

See Action, Slide Lock.


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.


ACTION, AUTOLOADING

See Action, Semiautomatic.


ACTION, AUTOMATIC

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.


ACTION, BALLARD

A type of dropping block, single shot action.


ACTION, BARRELED

A combination of barrel and receiver or frame and breech bolt together with the other parts of the mechanism by which a firearm is loaded, fired and unloaded. Usually a complete firearm less its stock.


ACTION, BLOW-FORWARD

A design for semiautomatic or automatic firearms, wherein the breech block is stationary and the barrel moves forward by gas pressure to open and eject the cartridge and recycle the action.


ACTION, BLOWBACK

A design found in semiautomatic and automatic firearms where the inertia of some component, usually supplemented with a spring, is the main locking force and no mechanical locking of the breech occurs.


ACTION, BOLT

A firearm in which the breech closure is: in line with the bore at all times; manually reciprocated to load, unload and cock; and is locked in place by breech bolt lugs engaging abutments usually in the receiver. There are two principle types of bolt actions, i.e., the turn bolt and the straight pull type.


ACTION, BOX LOCK

A design in which the hammer and hammer springs are located within the frame and the trigger assembly is in the lower tang.


ACTION, BREAK-OPEN

See Action, Top-Break.


ACTION, DELAYED BLOWBACK

An action which utilizes a mechanical means in conjunction with bolt mass to gain additional delay prior to bolt opening. Also called Retarded Blowback.


ACTION, DOUBLE

A handgun mechanism in which a single pull of the trigger first cocks and then releases the hammer.


ACTION, DROPPING BLOCK

An action in which the breech block moves vertically, or nearly so, inside of the receiver walls. Also called a falling block.


ACTION, FALLING BLOCK

An action in which the breech block moves vertically, or nearly so, inside of the receiver walls. Also called a dropping block.


ACTION, HINGED FRAME

A design wherein 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 or side lever.


ACTION, LEVER

A design wherein the breech mechanism is cycled by an external lever generally below the receiver.


ACTION, LOCKED BREECH

Any action wherein the breech bolt is locked to the barrel or receiver, through a portion or all of the recoiling motion.


ACTION, OPEN BREECH

A type of action wherein the breech bolt is held open until the trigger is pulled.


ACTION, PIVOTING BLOCK

An action in which the breech block pivots in an arc to expose or lock the breech.


ACTION, PUMP

See Action, Slide.


ACTION, RECOIL OPERATED

See Recoil Operated.


ACTION, ROLLING BLOCK

Single shot action in which a breech block and hammer each rotate about separate transverse pins in the receiver. The two members are swung rearward, away from the barrel breech to load the mechanism 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.


ACTION, SEMIAUTOMATIC

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 Action,Blowback and Action, Delayed Blowback. For Recoil Operated: See Recoil Operated. For Gas Operated: See Gas Operated.


ACTION, SIDE LOCK

A design in which the firing mechanism is attached to a side plate rather than being integral with the frame or trigger plate.


ACTION, SINGLE

An action requiring the manual cocking of the hammer or striker before sufficient pressure on the trigger releases the firing mechanism. The trigger performs the simple action of holding the hammer in position until pulled.


ACTION, 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.


ACTION, SLAVE

A special substitute action used for testing a barrel or barrels.


ACTION, SLIDE

A firearm which features a moveable forearm which is manually actuated in motion parallel to the barrel. Forearm motion is transmitted to a breech bolt assembly which performs all the functions of the firing cycle assigned to it by the design. This type of action is prevalent in rimfire rifles and shotguns and to a lesser extent in centerfire rifles. Also known as Pump Action or Trombone Action.


ACTION, SLIDE LOCK

The part of a mechanism, normally found on slide action firearms that locks the forearm/slide mechanism in the forward position.


ACTION, STRIPPED

A receiver or frame of a firearm from which all parts have been removed.


ACTION, TOP-BREAK

A design in which the barrel or barrels are connected to the frame by a hinge-pin below the barrels. Upon release of the locking mechanism, usually by a top, side or under-lever, the barrel or barrels rotate around the hinge-pin away from the standing breech.


ACTION, TRAP DOOR

This action has a top-hinged breech block that 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.”


ACTION, TROMBONE

See Action, Slide.


ACTION, TURN-BOLT

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.


ACTION, UNDER-LEVER

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.


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.


ADAPTER

1. A device used to alter the use or functioning of a firearm. Most general use of an adapter permits the use of smaller caliber ammunition in a firearm designed for a larger caliber. See Chamber, Auxiliary.
2. A GRIP ADAPTER alters the size or shape of the handle portion of apistol or revolver. Most generally used where a handgun is used for target practice.


AIM

The act of aligning the sights of a firearm on a target.


AIMING POINT

A point on the target upon which the sights are aligned.


AIR GAGE

A pneumatic device for measuring diameters.


AIR GUN

See Gun, Air.


AIR PISTOL

See Pistol, Air.


AIR RESISTANCE

The resistance of air to the passage of a projectile in flight.


AIR RIFLE

See Gun, Air.


AIR SPACE

The volume in a loaded cartridge or shotshell not occupied by the propellant or the bullet, wads or shot. Sometimes called Ullage.


AIR SPIRAL

The term used to describe the corkscrew-like flight path of a bullet.


ALIGN

To bring the front and rear sights on a gun into line with the axis of the bore.


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, SMALL ARMS

A military term for ammunition for firearms with bores not larger than one inch.


AMMUNITION, BALL

A term generally used by the military for a cartridge with a full metal jacket or solid metal projectile (bullet).


AMMUNITION, FIXED

A metallic cartridge or shotshell that is complete and ready o use.


AMMUNITION, LIVE

A cartridge or shotshell prior to being fired that is assembled with a live primer, an appropriate propellant and projectile or shot charge.


AMMUNITION, LOT

A term generally used by American sporting ammunition manufacturers for denoting same day conditions used to load a batch of ammunition.


AMMUNITION, MATCH

Ammunition made specifically for match target shooting. Produced with special controls to assure maximum uniformity of cartridge performance.


AMMUNITION, METALLIC

A generic term for rimfire and centerfire ammunition derived from their metallic cases.


AMMUNITION, NATIONAL MATCH

Ammunition produced by 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.


AMMUNITION, REFERENCE

Ammunition use in test ranges to evaluate test barrels, ranges and other velocity and pressure measuring equipment. May also be used as a control sample by which other characteristics are compared, such as accuracy, patterns, etc.


AMMUNITION, SERVICE

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.


AMMUNITION, SUB-CALIBER

A cartridge having a projectile smaller than is standard for the firearm in which it is used.


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

See Fore-End, Anson Fastening.


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.


APERTURE SIGHT

See Sight, Aperture.


ARM

1. To charge or load a firearm.
2. Contraction of “firearm.”


ARMS, SMALL

Generally a military term. Fully automatic weapon capable of being carried by a person and fired without additional mechanical support.


ASSEMBLY

Any collection of mutually operating parts housed together to form a single unit which may be a subassembly or a principle assembly.


AUTO

An expression sometimes used for autoloader or automatic firearm. Should not be confused with semi-automatic.


AUTOLOADING

See Action, Semi-Automatic. Also called Autoloader or Self-Loader.


AUTOMATIC

See Action, Automatic.


AUTOMATIC FEED MECHANISM

See Feed Mechanism, Automatic.


AUTOMATIC FIRE

See Pistol, Automatic. See Rifle, Automatic.


AUTOMATIC PISTOL

See Pistol, Automatic.


AUTOMATIC RIFLE

See Rifle, Automatic.


AUTOMATIC SAFETY

See Safety, Automatic.


AUXILIARY CARTRIDGE OR CHAMBER

See Chamber, Auxiliary.


AXIS OF BORE

See Bore Axis.


AXIS PIN

See Cylinder pin.