Letter B

The Definition of Breech

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Breech

The rear end of the barrel into which the cartridge is inserted


19 Other Firearms Definitions You Need To Know


Reflector Sight

A generally non-magnifying optical device that has an optically collimated reticle, allowing the user to look through a partially reflecting glass element and see a parallax free cross hair or other projected aiming point superimposed on the field of view. Invented in 1900 but not generally used on firearms until reliably illuminated versions were invented in the late 1970s (usually referred to by the abbreviation "reflex sight").

Gas Port

A small hole in the barrel of a gas-operated firearm through which expanding gases escape to power the autoloading system.

Clicks

A unit of adjustment for a sight.

Annulus

A tiny circular recess at the base of a cartridge case surrounding the primer pocket. Recoil from fired cartridges invariably impress a discernable ring on the breech or bolt face of a firearm, providing some evidence of the amount of use it has seen.

Leading

Fouling of a firearm bore by metal particles from bullets adhering to the metal surface caused by heat or friction.

Gas Vent

A passage built into a firearm to allow the safe conduct of unexpected gas, as from a pierced primer, to minimize damage both to the gun and to the shooter.

Trigger Control

Not putting your finger on the trigger until your sights are on target, then pulling the trigger smoothly, and following through by realigning the sights before allowing your finger to come off the trigger.

GCA

Gun Control Act of 1968. It is a U.S. federal law that regulates the firearms industry and firearms owners. It primarily focuses on regulating interstate commerce in firearms by generally prohibiting interstate firearms transfers except among licensed manufacturers, dealers and importers. It also prohibits all convicted felons, drug users and the mentally ill from buying guns amd raised the age to purchase handguns from a federally licensed dealer to 21.

Mainspring

A strong spring which activates the striker or hammer of a firearm.

Comb

The top of a gun's stock, where a shooter rests his cheek when mounting a gun. As it is the top of the stock that determines the position of one's eye, and one's eye is the rear sight on a shotgun, the position of the comb is very important in determining the proper fit of a shotgun.

POI

Abbreviation for Point of Impact

Hollow-Point Bullet

A type of expanding bullet with a concavity in its nose to increase expansion on penetration of a solid target. Some hollow-point's are also designed to fragment as they expand. They are least likely to over-penetrate the target and harm an innocent bystander. Commonly used for self-defense.

JSP

Abbreviation for jacketed soft point

Cock

The term referring to the action of manually drawing the hammer back against its spring until it becomes latched against the sear, or sometimes the trigger itself, arming the hammer to be released by a subsequent pull of the trigger. Some external hammers, and all internal hammers, may be cocked simply by pulling the trigger

Bore Diameter

The measurement from one side of the bore to the other. In a rifled barrel this means measurement of the bore before the rifling grooves are cut.

Fouling Shot

A fouling shot is a shot fired through a clean bore, intended to leave some residue of firing and prepare the bore for more consistent performance in subsequent shots. The first shot through a clean bore will behave differently from subsequent shots through a bore with traces of powder residue, resulting in a different point of impact.

Gunpowder

Also called black powder, gunpowder is a mixture of sulfur, charcoal, and potassium nitrate. It burns rapidly, producing a volume of hot gas made up of carbon dioxide, water, and nitrogen, and a solid residue of potassium sulfide. Because of its burning properties and the amount of heat and gas volume that it generates, gunpowder has been widely used as a propellant in firearms and as a pyrotechnic composition in fireworks. The term gunpowder also refers broadly to any propellant powder. Modern firearms do not use the traditional gunpowder (black powder) described here, but instead use smokeless powder.

Muzzleloader

The earliest type of gun, now also popular as modern-made replicas, in which blackpowder and projectile(s) are separately loaded in through the muzzle. The term is often applied to cap-and-ball revolvers where the loading is done not actually through the muzzle but through the open ends of the cylinder's chambers.

Intercepting Sear

A second sear, poised just behind a second notch in the hammer. It is possible that when a cocked firearm is dropped or sharply jarred, a single sear could jump out of its notch and the hammer could fall, firing the gun accidentally. In this event, an intercepting sear would engage before the hammer could fall completely, preventing an accidental discharge. On a gun with intercepting sears, only by pulling the trigger are both sears moved out of the way simultaneously, allowing the gun to fire. Intercepting sears are usually found on better sidelock actions. They are sometimes found on best boxlocks, and can be recognized by an extra screw behind the action fences, in addition to the usual two screws (or pins) along the lower rear of the receiver.