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


Bolt Face

The forward end of the bolt which supports the base of the cartridge and contains the firing pin.

Primer Pocket

The counter bore in the center of the base of a centerfire cartridge casing in which the primer assembly is seated.

DA

Abbreviation for Double Action

Electronic Firing

The use of an electric current to fire a cartridge, instead of a percussion cap. In an electronic-fired firearm an electric current is used instead to ignite the propellant, which fires the cartridge as soon as the trigger is pulled.

Breech Pressure

The amount of rearward force exerted by the propellant gases on the bolt or breech of a firearm action or breech when a projectile is fired. The applied force has both magnitude and direction, making it a vector quantity. This is also known as Bolt Thrust on firearms that are Bolt Action

Rifle

A shoulder-fired long gun which has a rifled barrel.

Muzzle Velocity

The speed of a projectile or a load of shot at the point that it exits the muzzle of a firearm, normally expressed feet per second.

Penetration

The distance travelled by a projectile from the point where it strikes the target to the point where it stops.

Handspanner

German for Hand-Cocking or Cocker/De-Cocker. A type of action on a break-open gun or rifle where, in place of a traditional top tang safety, a somewhat more robust tab is fitted. Normally such a gun is carried in the field loaded, but with the action not cocked, an exceedingly safe condition. Then, when ready to fire, the shooter, instead of pushing a safety tab forward, pushes this larger tab forward, cocking the mainspring, making the gun ready to fire. Then, if the shot is not taken, he may simply slide this tab rearwards again, de-cocking the gun and returning it to the still-loaded, but very safe position.

Sectional Density

The relationship between a bullet's weight and its diameter. A long bullet, such as the original 7.62x54R loading for the Mosin Nagant 91/30, will have a high sectional density and consequently greater penetration than a shorter bullet of similar construction. A shorter bullet with less sectional density will have relatively less penetration, but greater knockdown power.

Six Gun

A slang term for a revolver that holds siz rounds. Usually referring to cowboy style revolvers.

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.

Shooting Sticks

A pair of slender and easily-carried wooden dowels or sticks, which when held, crossed, in the fingers of the left hand while also supporting the forend of a rifle, usually shooting offhand, provides somewhat enhanced stability for a more accurate shot.

Malfunction

A misfeed or other failure to fire which can be cleared on the spot and without tools.

Adjustable Trigger

A trigger that can be easily adjusted by the user. Adjustable triggers are common on specialized target-shooting firearms.

Bullpup

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

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.

Lockplate

A metal plate on which the firing mechanism is mounted on percussion and earlier firearms.

Takedown

A firearm that can be separated into (at least) two subassemblies in order to make a shorter package than when put together, without tools. There is no specific requirement regarding how this disassembly must be accomplished; the mechanical design is up to the creativity of the maker. This arrangement allows for more convenient transportation of a firearm, but with rifles, where the action normally separates from the barrel, usually at a small sacrifice in accuracy. Takedown firearms can also be called take-apart firearms. Good examples of a takedown guns are the Henry AR-7 Survival Rifle, the Ruger 10/22 Takedown or the TNW Aero.