Letter A

The Definition of Aperture Sight

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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.


19 Other Firearms Definitions You Need To Know


Six Gun

A slang term for a revolver that holds siz rounds. Usually referring to cowboy style revolvers.

Straddle Floorplate

A hinged plate covering the bottom of a rifle magazine and extending rearward on either side of the triggerguard. This design allows it to be more securely fastened for one more imperceptible step towards total reliability.

Mushroomed Bullet

A description of a bullet whose forward diameter has expanded after penetration.

Kentucky Rifle

Usually referred to as a Kentucky Long Rifle or simply Longrifle, the Kentucky Rifle is a flintlock rifle with a long barrel and short, crooked stock. It is widely believed to be a largely unique development of American rifles that was uncommon in European rifles of the same period. The Kentucky Long Rifleis an early example of a firearm using rifling, (spiral grooves in the bore). This gave the projectile, commonly a round lead ball, a spiraling motion, increasing the stability of the trajectory. Rifled firearms saw their first major combat usage in the American colonies during the Seven Years war, and later the American Revolution in the eighteenth century.

ATF

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

Gauge

System of measurement for the internal bore diameter of a smooth-bore firearm based on the diameter of each of that number of spherical lead balls whose total weight equals one pound. The internal diameter of a 12 gauge shotgun barrel is therefore equal to the diameter of a lead ball weighing 1/12 pound, which happens to be .729" (Or in British: Bore.) The Gauge/Bore system is also used, by convention, to describe the internal barrel diameter of large-bore, 19th century, English, single-shot and double-barrel rifles.

Throat

The beginning of the bore of a rifled firearm. The transition between the chamber and the rifling. The area most vulnerable to erosion from high velocity cartridges.

MOA

Abbreviation for Minute Of Angle

Line Of Bore

An imaginary straight line through the centre of the bore of a firearm extending to infinity.

Range Finder

A device used to determine the range to a target. Many range finders work by bouncing a laser beam off the target or nearby object and measuring the time for the reflection to arrive back at the instrument. It is also possible to use various passive optical devices such as a mil-dot telescopic sight.

Misfire

The condition of a cartridge not firing when an attempt to fire it is made. It can be caused by either a defective cartridge or a defective firearm. The term is frequently misused to indicate a Negligent Discharge of a firearm.

Receiver

The housing for a firearm's breech (portion of the barrel with chamber into which a cartridge or projectile is loaded) and firing mechanism. In semi-automatic handguns and revolvers, this part is typically called the frame.

Mauser Safety

A small lever mounted to the cocking piece of a Mauser 98 action (and its copies such as the Springfield 1903), rotating on a longitudinal axis from left (Fire), up to the top (Safe, but allowing bolt movement), and over to the right (Bolt and firing pin locked Safe). While commendable for locking the firing pin instead of just the trigger, its up-and-over arc of operation requires a scope to be mounted awkwardly high. Paul Mauser is not to be blamed; when his safety was developed, telescopic sights were in such infancy as not to be worthy of mainstream consideration.

Self-Opening

Attribute of a break-open gun whereby the barrels drop down simply by pressing the toplever without muscling them open manually. The Holland & Holland system utilizes a coil spring within a cylindrical housing mounted just ahead of the forward lump to urge the barrels open. The Purdey system utilizes residual energy remaining in the mainspring after the gun has been fired. Both systems enable a shooter to load more quickly when birds are coming fast.

Percussion Cap

A small metal explosive-filled cup which is placed over the nipple of a percussion firearm. As the cap is struck by the hammer, it explodes and sends a flame through the flashhole in the nipple to the main powder charge.

Lands

In the rifling of a bore, the uncut portions of the barrel's inner surface left after the rifling grooves have been cut into the metal. In other words, the raised portion of rifling.

Lever Action

A type of firearm action which uses a lever located around the trigger guard area, (often including the trigger guard itself) to load fresh cartridges into the chamber of the barrel when the lever is worked.

Penetration

The distance travelled by a projectile from the point where it strikes the target to the point where it stops.

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.