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


Head

Head [of a Stock]. The forward end of a buttstock, where it meets the receiver and accepts the bulk of the gun's recoil when fired.

Leading

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

Off Hand

To shoot while standing and without bracing against anything. Sometimes it can also mean to shoot with your non-dominant hand.

Cylinder Drum

On a revolver, a spring activated device housed in the bottom of the frame beneath the cylinder that engages alignment notches in the cylinder. It stops the cylinder's rotation and holds it in place each time a chamber in the cylinder is in alignment with the barrel.

Dram

A unit of measure traditionally used for black powder shotgun charges. Today, used for smokeless powders on the basis of the new propellant's equivalent performance to that weight of black powder. Thus, a shotgun shell marked 3 - 1 1/8 would be loaded with the smokeless powder equivalent of 3 drams of black powder, and with 1 ounce of shot. 1 Dram = 1/16 ounce = 437.5 grains.

Ejector Star

On a revolver, the collective ejector, manually operated through the center of an opened cylinder, when activated, clears all chambers at once.

Parabellum

Latin word meaning "for war." It is actually the proper name of the semiautomatic pistol commonly known in the USA as the "Luger. Because of that pistol and the ammunition created for it, the common 9mm cartridge used nowadays is also known as 9mm Parabellum or 9mm Luger."

NFA

National Firearms Act of 1934. Enacted on June 26, 1934, currently codified as amended as I.R.C. ch. 53, is an Act of Congress in the United States that, in general, imposes a statutory excise tax on the manufacture and transfer of certain firearms and mandates the registration of those firearms. The Act was passed shortly after the repeal of Prohibition. The NFA is also referred to as Title II of the Federal firearms laws.
The NFA includes:

  • Requires the registration of all fully automatic firearms.
  • Requires the registration of all "sawed off" rifles and shotguns.
  • Requires the registration of firearm silencers.
  • Imposes a $200 transfer tax on the above items.

Choke Tubes

Short, interchangeable cylinders, of subtly different internal tapers, that screw into a threaded recess at the muzzle of a shotgun. By inserting different choke tubes, one can alter the shot pattern thrown by the gun.

Pistol

Synonymous with "handgun." A gun that is generally held in one hand. It may be of the single-shot, multi-barrel, repeating or semi-automatic variety and includes revolvers.

Casehardening

A heat-treating process that incorporates carbon into the surface molecular structure of the steel, providing a hard-wearing surface without making the entire receiver brittle. The parts to be casehardened are packed in a crucible with carbon-rich media such as bone meal and charcoal, heated to bright orange, about 1800F, then quenched in bubbling oil. Also called Carbonizing.

Boresight (Bore Sight)

Crude adjustments made to an optical firearm sight, or iron sights, to align the firearm barrel and sights. This method is usually used to pre-align the sights, which makes zeroing (zero drop at XX distance) much faster.

Sights

The device that aids the eye in aiming the barrel of a firearm in the proper direction to hit a target.They can be a mechanical, optical, or electronic device. Iron sights or sometimes as open sights, consist of specially-shaped pieces of metal placed at each end of the barrel. The sight closest to the muzzle end of the gun is called the front sight, while the one farthest from the muzzle (and nearest to the shooter) is called the rear sight.

Failure To Extract

A semi-automatic firearm malfunction in which the extractor fails to move the empty case out of the way as the slide travels back. A failure to extract often causes double-feed malfunction.