Letter A

The Definition of ACP

Arsenal Exchange - Firearms Classifieds - Industry Directory

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.


19 Other Firearms Definitions You Need To Know


Ears

Slang for hearing protection. Applies to either muffs or plugs.

Point of Impact

The point where the projectile from a firearm hits.

Muzzle

The open end of the barrel from which the projectile exits.

Rail Mount

Any type of accessory that can be attached to a firearm's rail.

Magnum

From the Latin for "more." A term indicating a relatively heavily loaded metallic cartridge or shotshell and a gun safely constructed to fire it. It generally indicates a round which cannot be interchanged with other loadings of the same caliber (for example, a .22 Magnum shell does not fit within a firearm designed to fire .22 Long Rifle ammunition).

Fixed Ammunition

A complete cartridge of several obsolete types and of today's rimfire and center-fire versions

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.

Falling Block

A type of action used primarily for single shot rifles whereby some kind of lever actuates a breechblock, moving it downwards in a vertical recess to expose the chamber. May have visible or enclosed hammer. For any given barrel length, it allows a shorter overall rifle length compared to a bolt action because no space is taken up by the forward-and-back cycling of the bolt. Most of the better British makers produced them in limited numbers around the turn of the last century, the Farquharson being the most iconic. Perhaps the best-known falling block action today is the Ruger No.1.

Interrupted Thread

A screw with about half of its threading removed in longitudinal sections. Often used at the breech end of a takedown firearm's barrel. When the barrel's interrupted female threads are inserted into the receiver's complementary interrupted male threads, only a partial rotation is necessary for assembly rather than many full turns.

Checkered Butt

Checkering, applied to the otherwise-unfinished butt end of a gunstock.

Muzzle Energy

The power of a projectile or a load of shot at the point that it exits the muzzle of a firearm, normally expressed in foot-pounds.

Eye Relief

The distance that equates the exit pupil size of a rifle scope's ocular lens to the entrance pupil of the user, in order to achieve the largest, unvignetted view. This distance must be sufficient to ensure that the ocular rim of the scope does not lacerate the shooter's eyebrow upon recoil. And, the scope should be positioned so that eye relief is suitable when the rifle is comfortably mounted.

Crosshairs

The cross-shaped object seen in the center of a firearm scope. Its more-proper name is reticle.

Trigger Pull Weight

The ammount pressure needed (measured in pounds) for the trigger finger must put on the trigger before the gun will fire. Trigger pull weight is measured by the number of pounds and ounces of pressure required to pull the trigger past the break.

Cannelure

A groove or indention around the circumference of a bullet. Its purpose is to permit the cartridge casing to be crimped tightly against the bullet shank to hold it firmly to the casing. A groove or indention around the circumference of a bullet. Its purpose is to permit the cartridge casing to be crimped tightly against the bullet shank to hold it firmly to the casing.

Gape

The degree to which the barrel(s) of a break-open gun drop down; the size of the opening space, which should be sufficient to allow for ease of loading, unloading and properly-functioning ejection. A good gape is easier to achieve on a side-by-side than an over & under where the bottom barrel is well-enclosed by the action body.

Open Tip Match

A rifle projectile made with the tip of the bullet open as a means of increasing accuracy as compared to standard military bullets that are made with a closed tip and an open base. The are not designed to expand like a hollow point bullet but may fragment.

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.

Patch Box

Covered compartment in the buttstock of a rifle used to carry patches or other small items.

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