Letter A Firearms Glossary

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Accidental Discharge

An unexpected and undesirable discharge of a firearm caused by circumstances beyond the control of the participant(s) such as a mechanical failure or parts breakage. There are very, very few firearms related "accidents" and if the "Three Rules" are followed there will hopefully be no injury. Accidental Discharge should not be confused with "Negligent Discharge".

ACP

The abbreviation for Automatic Colt Pistol. It is commonly used to designate specific calibers, particularly those which were originally designed by John Moses Browning for the Colt Firearms Company which are a type of rimless pistol cartridge designed mainly for use in semi-automatic pistols. The most common ACP calibers are .25 ACP, .32 ACP, .380 ACP and .45 ACP.

Action

The working mechanism of a firearm involved with presenting the cartridge for firing, and in removing the spent casing and introducing a fresh cartridge. For example some of the most common types of Actions are single, double, bolt, lever and pump.

AD

Abbreviation for Accidental Discharge

Adjustable Stock

The stock is the wooden, polymer, or metal handle of a long gun that extends from the trigger back to where the gun is braced against the shoulder. An adjustable stock is one that can be easily lengthened or shortened to fit shooters of different sizes.

Adjustable Trigger

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

AE

Abbreviation for Arsenal Exchange or ArsenalExchange.com. Example in a sentence is "Have you seen the latest postings on AE?
AE is also the abreviation for Action Express. .50 Action Express (.50 AE) is a large caliber handgun cartridge. It was developed in 1988 by Evan Whildin of Action Arms.

Airgun (Air Gun)

A variety of pneumatic gun that propels projectiles by means of compressed air or other gas, in contrast to firearms, which use a propellant charge. Both the rifle and pistol forms (air rifle and air pistol) typically propel metallic projectiles, either pellets, or BBs. Certain types of air guns, usually rifles, may also propel arrows.

Airsoft (Air Soft)

A type of airgun that shoots spherical non-metallic pellets.

AK

AK stands for Avtomat Kalashnikova (Kalashnikov rifle when translated into English). When someone says "an AK" they are usually referring to the AK-47 rifle which was originally designed in Russia by Mikhail Kalashnikov.

Ambi

Short for the word Ambidextrous. Meaning that a feature of a firearms can be used by either hand, for example ambi-safety, ambi slide catch or ambi mag release.

Ammo

Slang word abreviation for Ammunition.

Ammunition

The "packaged" components that are needed in order to fire in a case or shell holding a primer, (which produces the spark) a charge of propellant (gunpowder) and a projectile (bullets, slug or pellets.) Sometimes called "fixed ammunition" to differentiate from the individual components placed separately in muzzleloaders. A single unit of ammunition in modern firearms is called a cartridge. The units of measure for quantity of ammunition is rounds. There are hundreds of sizes of ammunition, examples include .223 Remington, 9mm Luger, 30.06, .308 Winchester, .300 Winchester Magnum, and .50 Browning Machine Gun (BMG). The ammunition used must match the firearm.

Annulus

A tiny circular recess at the base of a cartridge case surrounding the primer pocket. Recoil from fired cartridges invariably impress a discernable ring on the breech or bolt face of a firearm, providing some evidence of the amount of use it has seen.

Anson & Deeley Action

A type of internal hammer side by side shotgun boxlock action. It was patented in 1875 and is the essence of simplicity utilizing only two springs and three moving parts (per barrel). One of the most successful action designs ever, and still produced to this day by most SxS shotgun manufacturers.

Antique Firearm

Defined according to Section 921 (a) (16), Title 18, U.S.C. as:

A. any firearm (including any firearm with matchlock, flintlock, percussion cap, or similar type of ignition system) manufactured in or before 1898; and
B. any replica of any firearm described in subparagraph (A) if such replica (i) is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition, or (ii) uses rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade.

Aperture Sight

Also known as peep sights, range from the ghost ring sight, whose thin ring blurs to near invisibility (hence ghost), to target aperture sights that use large disks or other occluders with pinhole-sized apertures. In general, the thicker the ring, the more precise the sight, and the thinner the ring, the faster the sight.

AR

Contrary to some people's belief, AR does NOT stand for Assault Rifle. The designation AR stands for the original designing company ArmaLite.
An AR is a firearm platform originally designed by ArmaLite and built by Colt, an AR is a lightweight, intermediate cartridge magazine-fed, air-cooled rifle with a rotating lock bolt, actuated by direct impingement gas operation or long/short stroke piston operation. It has been produced in many different versions, including numerous semi-automatic and selective fire variants. It is manufactured with extensive use of aluminum alloys and synthetic materials. Types of ARs include AR-15, AR-10 and AR-7.

Armor-Piercing Ammunition

An armor-piercing shell must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge.

Arsenal

An established place where firearms and ammunition are stored, repaired, or manufactured. The term is misused by the media to mean more than one firearm or any quantity of ammunition, as in "they found an arsenal."

Arsenal Exchange

Arsenal Exchange, ArsenalExchange.com is the number one free firearms classified ad and gun industry directory on the internet. Not only does Arsenal Exchange have firearms related classified ads to allow people to advertise their guns, ammunition and firearms related services for free, they have combined that with an all-inclusive self-service free firearms industry directory.

Articulated Front Trigger

A spring-loaded hinged front trigger on a dual trigger side by side or over under shotgun, built to cushion its impact on one's trigger finger as the gun recoils when the rear trigger is pulled.

Assault Rifle

Assault Rifles and Assault Weapons do not exist. The terms Assault Rifle and Assault Weapon are made up terms by the anti-gun lobby to describe black rifles with forward grips that you might see in the movies like an AR-15 or an AK-47. Assault Rifles do not exist because a gun cannot assault anything, they are machines that need to be operated by a person.

ATF

Short abbreviation for the Bureau of Alcohol, Tobacco, Firearms and Explosives

Autoloader

A firearm that automatically loads the next cartridge to be fired into the chamber either upon the pull of the trigger in an open bolt design or upon the firing of the previous round in a close bolt design.
Autoloader should not be confused with Automatic or Semi-Automatic since the term Autoloader only applies to how the next round is chambered not how many rounds can be fired per trigger pull. All Automatic and Semi-Automatic firearms are autoloaders. Revolvers, bolt action, lever action and pump action firearms are not autoloaders.

Automatic

A type of firearm which, utilizing some of the recoil or some of the expanding-gas energy from the firing cartridge, cycles the action to eject the spent shell, to chamber a fresh one from a magazine, to cock the mainspring and to fire again. Such a firearm will fire continuously as long as the trigger is held back, until the magazine is empty. A machine gun. A firearm thus activated, but which shoots only one bullet with each separate pull of the trigger, while often erroneously referred to as "automatic" is properly termed Semi-Automatic.