Letter J

The Definition of Jacket

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Jacket

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


19 Other Firearms Definitions You Need To Know


Expanding Bullet

An expanding bullet is a bullet designed to expand on impact, increasing in diameter to limit penetration and/or produce a larger diameter wound. The two typical designs are the hollow point bullet and the soft point bullet. See also Dum-Dum Bullet

Explosive

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

Wildcat Cartridge

A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic (such as the power, size or efficiency) of an existing commercial cartridge. Developing and using wildcat cartridges does not generally serve a purpose in military or law enforcement; it is more a hobby for serious shooting, hunting, gunsmithing and handloading enthusiasts, particularly in the United States. There are potentially endless amounts of different kinds of wildcat cartridges: one source of gunsmithing equipment has a library of over 6,000 different wildcat cartridges for which they produce equipment such as chamber reamers.

COF

Abbreviation for Course of Fire.

Line Of Sight

An imaginary straight line from the eye through the sights of a firearm to the target.

Quad Barrelled

A gun, typically artillery, with four barrels, such as the ZPU

Scope Blocks

A pair of small dovetailed steel bases, screwed usually one to the barrel and one to the front receiver ring of a rifle, to accept mounts for target scopes such as the Unertl where the scope is allowed to move forward in the rings under the recoil of the rifle and which typically carry the windage and elevation adjustments in the mount.

Headspace Gauge

Plugs of hardened steel, precisely machined in relation to the standard dimensional specifications of a given cartridge, normally in sets of three: "GO", "No-Go" and "Field". By loading these plug-gauges into the chamber in succession, one can check that the action should close on the "Go" gauge. It should not close on the "No-Go" gauge, but might were enough force to be used. And, it absolutely should not close on the "Field" gauge.

Trigger Break

The point at which the trigger allows the hammer to fall, or releases the striker, so that the shot fires. The ideal trigger break is sudden and definite. "Like a glass rod" is the cliche term shooters use to describe the ideal crisp, clean break.

Snap Shot

A quick shot taken without deliberate aim.

Weaver Stance

In the Weaver stance, the body is bladed partly sideways in relation to the target rather than squared towards it (think boxing or martial arts fighter stance). The elbows are flexed and pointed downward. The strong-side arm is slightly straighter than the weak-side arm. Even though the legs are not square to tharget, the hips should be square to the target. The feet should be pointed at the target. The shooter pushes out with the gun hand, while the weak hand pulls back. This produces a push-pull tension which is the chief defining characteristic of the Weaver stance.

Drift

The departure of a bullet or shot charge from the normal line of flight. This can be caused by wind or the unbalanced spinning of the bullet.

Mag

Slang word for Magazine.

Rear Sight

The rear sight is placed at the end of the barrel nearest the shooter. It may be in the shape of a square notch, a U, a V, a ring, or simply two dots designed to be visually placed on either side of the front sight while shooting.

Colt

A firearms manufacturer started by Samuel Colt in 1855. Colt is most famous for the revolvers they invented and built in the 1800's and the semi-automatic pistol model 1911 designed by John Moses Browning, and for being the first manufacturer of the AR-15 type rifles.

High-Capacity Magazine

An inexact, non-technical term indicating a magazine holding more rounds than might be considered "average.".

Underwater Firearm

A firearm specially designed for use underwater.

Stock

The back part of a rifle or shotgun, excluding the receiver.

Repeater

A type of firearm capable of discharging multiple individual shots in sequence, fed from a magazine, via the operation a lever, bolt, slide or some other form of manual operation.