Letter J

The Definition of Jam

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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.


19 Other Firearms Definitions You Need To Know


Close Quarters Combat

a type of fighting in which small units engage the enemy with personal weapons at very short range, potentially to the point of hand-to-hand combat or fighting with hand weapons such as swords or knives.

ACP

The abbreviation for Automatic Colt Pistol. It is commonly used to designate specific calibers, particularly those which were originally designed by John Moses Browning for the Colt Firearms Company which are a type of rimless pistol cartridge designed mainly for use in semi-automatic pistols. The most common ACP calibers are .25 ACP, .32 ACP, .380 ACP and .45 ACP.

Bullpup

A firearm configuration where the magazine and action are behind the trigger.

Caseless Ammunition

A type of small arms ammunition that eliminates the cartridge case that typically holds the primer, propellant, and projectile together as a unit.

Snap Cap

An inert ammunition-shaped object, used in practice to simulate misfeeds and other malfunctions. Some folks also use them during dry fire practice to cushion the firing pin as it strikes.

Machine Gun

A fully automatic firearm that rapidly fires multiple rifle-caliber shots with a single pull of the trigger.

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.

Back Bored

A shotgun barrel that has a bore diameter increased beyond standard specifications, but less than the SAAMI maximum. Done in an attempt to reduce felt recoil, improve patterning, or change the balance of the shotgun.

Matchlock

A black powder muzzleloading firearm action which relies upon a serpentine or S-shaped piece of metal to hold a smoldering match. By pressing the lower end of the serpentine, the upper end holding the burning match contacts the priming powder in the pan.

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Jacket

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

BATF

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

Gain Twist

A form of rifling where the helical angle (pitch) sharpens progressively down the bore in the interest of maximizing the bullets ultimate rotational speed by initiating it slowly.

Shooting Range

A specialized facility designed for firearms practice.

Down Range

The area of a gun range where firearms are pointed when they are fired. The area of the range forward of the firing line.

Trigger Safety

An external, passive safety which can be found on the face of some trigger designs (most notably found on Glock firearms). It is intended to prevent the trigger from being pulled by objects which find their way into the trigger guard area.

Red Dot Sight

A type of reflector (reflex) sight for firearms that gives the uses a red light-emitting diode as a reticle to create an aimpoint.

Choke

A constriction at or near the muzzle of a shotgun barrel that affects shot dispersion.

Matched Pair

Two firearms that are manufactured identical in every way and are sequentially serial numbered and are sold as a set. The most common type of matched pair guns are cowboy style revolvers for a couple of reasons, both guns will feel exactly the same in the hands and they make the set more collectable.