Letter O

The Definition of Optical Sight

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Optical Sight

Usually a telescopic firearm sight.


19 Other Firearms Definitions You Need To Know


Magazine Safety

A mechanism that prevents the gun from being able to fire when the magazine is removed from the gun, even if there is still a round in the chamber.

Mirage

A tendency for layers of air of different temperatures near the warm ground to cause refraction in the line of sight and disturbance of the perceived point of aim.

Bore Axis

An imaginary line which runs right down the center of the handgun's barrel and out though the back end of the gun. A handgun may have a high bore axis, with the imaginary line running out into space well above the shooter's hand. Or it may have a low bore axis, with the imaginary line running either straight through the shooter's hand or just skimming the surface slightly above her hand. A high bore axis tends to create greater perceived recoil and more muzzle flip when firing the gun than does a low bore axis.

Shotgun Shell

The cartridge for a shotgun. It is also called a "shell," and its body is usually made of plastic (metal shotgun shells are very rare, paper shotgun shells are extinct) with a metal head. Small shotshells are also made for rifles and handguns and are often used for vermin control.

Twilight Sight

A rifle front sight with a extra-large, folding bead. Typically, in addition to the normal fine bead (which allows for more precision) the larger bead, while at a cost of potential accuracy, is more readily acquired in marginal light. Also called a Gloaming sight

Crown

The area inside the bore nearest to the muzzle.

EDC

Abbreviation for Every Day Carry

Burst Mode

A firing mode enabling the shooter to fire a predetermined number of rounds with a single pull of the trigger.

Cold Clean Bore

The first shot from a rifle that has been cleaned, and not fired recently may go to a different point of impact, for the same point of aim than a rifle that has been fired recently. This first shot is referred to as a shot from a cold, clean, bore.

Cannelure

A groove or indention around the circumference of a bullet. Its purpose is to permit the cartridge casing to be crimped tightly against the bullet shank to hold it firmly to the casing. A groove or indention around the circumference of a bullet. Its purpose is to permit the cartridge casing to be crimped tightly against the bullet shank to hold it firmly to the casing.

Explosive

Any substance (TNT, etc.) that, through chemical reaction, detonates or violently changes to gas with accompanying heat and pressure.

Disc-Set Strikers

Circular steel fittings, about 1/2 inch in diameter, screwed into the breech face of a gun and through which the firing pins pass. Firing pin bushings allow the convenient replacement of broken firing pins. They also allow the renewal of an older gun where, over the decades, leakage of high-pressure gas from corrosive primers has eroded the breech face around the firing pins; and replacing these bushings with new ones, slightly oversized can compensate for a situation where proper headspace has been compromised.

Semi-Automatic

A firearm designed to fire a single cartridge, eject the empty case and reload the chamber each time the trigger is pulled. It uses the energy from the fired shot to eject the empty case and feed the next round into the chamber.

Clip

A clip IS NOT a magazine. A clip is used to load a magazine.
A clip is a simple, disposable narrow spring-lined channel-rail that is used to store multiple rounds of ammunition together as a unit, ready for insertion into the magazine of a repeating firearm. This speeds up the process of loading and reloading the firearm as several rounds can be loaded at once, rather than one round being loaded at a time. The term clip commonly refers to a firearm magazine, though this usage is absolutely completely totaly 100% incorrect. In the correct usage, a clip is used to feed a magazine or revolving cylinder, while a magazine or a belt is used to load cartridges into the chamber of a firearm. in which cartridges are supplied for military weapons. The shooter positions the clip vertically above the firearm's magazine, then pressing down with the thumb, slides the cartridges from the clip and down into the magazine.

ATF

Short abbreviation for the Bureau of Alcohol, Tobacco, Firearms and Explosives

Self-Opening

Attribute of a break-open gun whereby the barrels drop down simply by pressing the toplever without muscling them open manually. The Holland & Holland system utilizes a coil spring within a cylindrical housing mounted just ahead of the forward lump to urge the barrels open. The Purdey system utilizes residual energy remaining in the mainspring after the gun has been fired. Both systems enable a shooter to load more quickly when birds are coming fast.

Damascus Barrels

Barrel tubes built up by twisting alternate strips of iron and steel around a fixed rod (mandrel) and forge-welding them together in varying combinations according to the intended quality and the skill of the maker. The rod was withdrawn, the interior reamed and the exterior filed until the finished tube was achieved. Damascus barrels may be recognized by any of a variety of twist or spiral patterns visible in the surface of the steel. Before the 20th century, barrels were typically built in this manner because gunmakers did not have the technology to drill a deep hole the full length of a bar of steel without coming out the side.

Plus P

Also spelled "+P" or "P+". Is small arms ammunition that has been loaded to a higher internal pressure than standard for it's caliber. Many calibers are available in both standard and +p or +p+ variants. Ammunition marked +p produces more power and higher pressures than the standard ammunition. Not all firearms are designed to handle the increased pressure consult your owner's manual or gun manufacturer before using +P ammunition.

Grip Safety

A passive, external safety typically located on the backstrap, which must be fully depressed to release the trigger. Most 1911-pattern pistols feature a grip safety.