Letter B

The Definition of Barrel

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A tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity. It is the tube through which the bullet or shot travels. The barrel serves the purpose of providing direction and velocity to the bullet.

19 Other Firearms Definitions You Need To Know

Blown Pattern

A shotgun pattern with erratic shot distribution, generally caused by gas escaping past the wads and getting into the shot.


Abbreviation for the Bureau of Alcohol, Tobacco, Firearms and Explosives

Cold Clean Bore

The first shot from a rifle that has been cleaned, and not fired recently may go to a different point of impact, for the same point of aim than a rifle that has been fired recently. This first shot is referred to as a shot from a cold, clean, bore.

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


Sloppy movement (slack) of a trigger before the actual point of let-off.

Buttplate (Butt Plate)

A plate which covers the butt. Some steel buttplates have trap doors covering a recess for storage of cleaning equipment.


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.

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.

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.

Primer Ring

Refers to a visible dark ring created by the primers in centerfire ammunition around the firing pin hole in the frame after much use.

Firing Line

A line, either imaginary or marked, from which people shoot their firearms down range.


In a handgun that does not have a hammer, the striker is a linear driven, spring loaded cylindrical part which strikes the primer of a chambered cartridge. The striker replaces both the hammer and firing pin found in hammer driven pistols.

Gas Port

A small hole in the barrel of a gas-operated firearm through which expanding gases escape to power the autoloading system.


To explode with great violence. It is generally associated with high explosives e.g. TNT, dynamite, etc., and not with the relatively slow-burning smokeless gunpowders that are classed as propellants.

Bolt Thrust

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.

Double-Barreled Shotgun

A shotgun with two barrels, usually of the same gauge or bore. The two types of double-barreled shotguns are over/under (abbreviated as O/U or OU), in which the two barrels are stacked on top of each other, and side-by-side (abbreviated as SxS), in which the two barrels sit beside each other. See photo at right for example of side-by-side double-barreled shotgun. For double-barreled guns that use one shotgun barrel and one rifle barrel, see combination gun.


The original small single-shot or multi-barreled pocket pistol designed and manufactured by Henry Deringer of Philadelphia. Derringers (spelled with two Rs) are called that because of the original desinger and anmufactuturer of that type of gun, Henry Deringer. To get around copyright infringment other designers and manufacturers spell the name with two Rs. However guns designed and built by Deringer are spelled with only one R

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.

Factory Ammo

Ammunition that has been assembled by a commercial vendor of ammunition and sold in retail stores. This is as opposed to Hand loads which have been assembled by individuals and are not typically sold.