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.
O
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.
OIL DENT
A shallow indentation in a cartridge case, generally caused by excessive oil:
a) present in dies during case manufacture
b) in re-sizing dies during handloading operations
c) in a chamber during firing
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.