Letter U

The Definition of Underhammer

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Underhammer

A type of lock in which the hammer pivots in a vertical arc, striking the nipple on the underside of the barrel. Since the nipple's flash channel goes straight into the powder at the breech end of the barrel, ignition time is very fast. For this reason, and because it gets the hammer out of the way, underhammer locks are commonly used on muzzleloading benchrest rifles which are used for target shooting, and where accuracy is the goal.


19 Other Firearms Definitions You Need To Know


Birdshot

A type of shotgun ammunition which uses very small pellets with individual projectiles of less than .24" in diameter designed to be discharged in quantity from the shotgun. The size of the shot is given as a number or letter-- with the larger number the smaller the shot size. It is so named because it is most often used for hunting birds. The finest size generally used is #9 which is approximately .08" in diameter and the largest common size is #2 which is approximately .15"

Overbore Capacity

Is that combination of caliber, barrel length, bullet weight, and case volume which does not allow the complete burning of the charge of ballistically correct powder within the volume of case and barrel.

Slide Bite

A phenomenon which is often grouped with hammer bite. In this case the web of the shooting hand is cut or abraded by the rearward motion of the semi-automatic pistol's slide, not by the gun's hammer. This most often occurs with small pistols like the Walther PPK and Walther TPH that have an abbreviated grip tang. This problem is exacerbated by the sharp machining found on many firearms.

Frizzen

The part of a flintlock action that receives the blow of the flint-tipped hammer, which then yields tiny molten fragments of steel ,sparks, which fall into the flashpan, igniting the priming charge and thence, through the touchhole, the main charge.

FOPA

Firearm Owners' Protection Act of 1986. It is a United States federal law that revised many provisions of the Gun Control Act of 1968. It bans civilian ownership of machine guns manufactured after May 19, 1986. Firearms made and registered before that date are not affected. The law limits the Bureau of Alcohol, Tobacco and Firearms from inspecting gun dealers more than once a year, with follow-up inspections allowed only The law also specifically forbids the government from creating a national registry of gun ownership.

Youth Rifle

A short, lightweight rifle. Some are small enough for a young child to easily handle, while others are large enough to perfectly suit teenagers, average-sized adult women, and small-statured adult males.

COF

Abbreviation for Course of Fire.

Frangible

A bullet that is designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of range safety, to limit environmental impact, or to limit the danger behind the intended target. Examples are the Glaser Safety Slug and the breaching round.

Railgun

A railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor.
Using a magnetic field powered by electricity, a rail gun can accelerate a projectile up to 52,493 feet (16,000 meters) per second.
A railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (at the end connected to the power supply), it completes the circuit. Electrons flow from the negative terminal of the power supply up the negative rail, across the projectile, and down the positive rail, back to the power supply.

Hammer Bite

The action of an external hammer pinching or poking the web of the operator's shooting hand between the thumb and fore-finger when the gun is fired.

Failure To Fire

Any malfunction that results in no shot fired when the trigger is pulled. Commonly caused by a failure to feed, bad ammunition or a broken firing pin.

Silencer

Improper term for a device that cuts down on the noise a firearm makes when it is shot. The correct term is suppressor. Silencers only exist in the movies.

Half grip

Round knob, semi pistol grip.

Ballistics

The science of cartridge discharge and the bullet's flight. Internal ballistics deals with what happens inside of a firearm upon discharge. External ballistics is the study of a projectile's flight, and terminal ballistics is the study of the impact of a projectile.

Fouling

The accumulation of unwanted material on solid surfaces. The fouling material can consist of either powder, lubrication residue, or bullet material such as lead or copper.

Lock Time

The interval of time between trigger release and the detonation of the primer. Generally, the faster the lock time the better, because this makes it easier to shoot accurately.

Speed Strip

A flat piece of rubber which holds revolver cartridges preparatory to loading them into the revolver's cylinder. Similar to a moon clip

Stovepipe

Failure of a spent case to completely eject from a semi-automatic firearm. The case usually stands on end while lodged in the ejection port.

Headstamp

Markings impressed into the base of a cartridge case, normally identifying the maker's name, the cartridge calibre designation, and sometimes the date.