Letter J Firearms Glossary

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Jacket

A metal, usually copper, wrapped around a lead core to form a bullet.

Jam

A malfunction which locks up the gun so badly that tools are required in order to fix it. Sometimes used to denote a simple malfunction, but many people make a distinction between a complete jam and a simple malfunction.

Jaws

The vise-like device on a flintlock hammer used to hold the flint.

Jeweling

A cosmetic process to enhance the looks of firearm parts, such as the bolt. The look is created with an abrasive brush and compound that roughs the surface of the metal in a circular pattern.

JSP

Abbreviation for jacketed soft point

Jump

The amount of change in the bore axis, measured both vertically and horizontally, while the projectile moves from the chamber to the muzzle when it is fired.


14 Other Firearms Definitions You Need To Know


Stovepipe

Failure of a spent case to completely eject from a semi-automatic firearm. The case usually stands on end while lodged in the ejection port.

Armor-Piercing Ammunition

An armor-piercing shell must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge.

Straddle Floorplate

A hinged plate covering the bottom of a rifle magazine and extending rearward on either side of the triggerguard. This design allows it to be more securely fastened for one more imperceptible step towards total reliability.

Rifle Bedding

A process of filling gaps between the action and the stock of a rifle with an epoxy based material.

BATF

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

Pair

Two shots fired very quickly with the use of the sights.

Firing Pin

A needle like metal part of a modern firearm that gives a vigorous strike to the primer initiating the firing of the cartridge.

Neck

The forward portion of a bottlenecked cartridge case. Also the portion of a rifle chamber in which the neck of the cartridge case rests.

Modern Isosceles

In the Modern Isosceles stance, the feet are roughly shoulder width apart, with the gun-side foot closer to the target than the off-side foot. The knees are flexed, and the entire body leans slightly toward the target. The shoulders are closer to the target than the hips, and the hips are more forward than the knees. The shoulders are rotated forward and the head, rather than being upright, is vultured down behind the sights. The entire body thus has an aggressively forward appearance, and is poised to move quickly if necessary.

Battery

Most firearms do not have literal batteries. But a firearm is said to be in battery when the breech is fully closed and locked, ready to fire. When the breech is open or unlocked, the gun is out of battery and no attempt should be made to fire it. A semi-automatic is out of battery when the slide fails to come all the way forward again after the gun has fired, making it dangerous or impossible to fire the next round. This condition can be created by a misfeed, a dirty gun, weak springs, the shooter's thumbs brushing against the slide, riding the slide, or any of several other causes.

Drilling

A three-barrel gun. Typically it has two shotgun barrels side by side on the top, with a third rifle barrel underneath. This provides a very versatile firearm capable of taking winged animals as well as big game. It also is useful in jurisdictions where a person is only allowed to own a single firearm.

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").

Silencer

Improper term for a device that cuts down on the noise a firearm makes when it is shot. The correct term is suppressor. Silencers only exist in the movies.

Skeet

A shotgun shooting sport in which the competitors attempt to break aerial targets directed toward them or crossing in front of them from different angles and elevations. It is an Olympic shooting sport.