Letter H

The Definition of Headspace

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Headspace

The distance, or clearance, between the base of a chambered cartridge and the breech face (or bolt face) of a firearm. This is a critical dimension, particularly in high powered rifles. If there is too little headspace, the bolt will not close. If there is too much headspace the cartridge will not be properly supported in the chamber and the cartridge will expand upon firing and may rupture, blasting high-pressure gas into the action and possibly into the body of the shooter. Headspace should be .003" - .006" in a centerfire rifle. It can be checked with a set of "Go and No-Go" gauges specific to the calibre in question. (See below.) With a standard cartridge, the headspace is registered by the shoulder, with a belted cartridge, the headspace is registered by the forward edge of the belt.


19 Other Firearms Definitions You Need To Know


Battery

Most firearms do not have literal batteries. But a firearm is said to be in battery when the breech is fully closed and locked, ready to fire. When the breech is open or unlocked, the gun is out of battery and no attempt should be made to fire it. A semi-automatic is out of battery when the slide fails to come all the way forward again after the gun has fired, making it dangerous or impossible to fire the next round. This condition can be created by a misfeed, a dirty gun, weak springs, the shooter's thumbs brushing against the slide, riding the slide, or any of several other causes.

Burst Mode

A firing mode enabling the shooter to fire a predetermined number of rounds with a single pull of the trigger.

Point of Impact

The point where the projectile from a firearm hits.

Keyhole

The tendency of a bullet to tip in flight and hit a target sideways, leaving a distinctly oblong hole. This destabilization of the spinning bullet in flight is typically caused by a bullet weight inappropriate for the rate of twist of the rifled barrel, an out-of-balance bullet or its having nicked an impediment such as a blade of grass, in flight.

Laser Sight

A laser sight is an alternative sighting device which enables the shooter to quickly and accurately see where the firearm is aimed even when lighting or other conditions prevent using the gun's normal sights. Lasers may be located within the grips, hung from accessory rails at the front end of the gun, or placed within the firearm.

Slug Gun

Slang for a shotgun which is set up specifically to fire a slug (a large, single projectile) rather than shot (multiple projectiles contained within a single shell).

Peep Sight

An alternate name for Aperture Sight.

Sabot

An oversized, lightweight housing that allows a sub-calibre projectile to be fired in a larger-diameter bore, usually in the interest of increased velocity. The sabot falls away from the actual projectile upon exiting the muzzle. For example, a hunter could use his .30-30 deer rifle to shoot small game with .22 centerfire bullets.

Erosion

The wearing away of a barrel's metal surface by a bullet or shot charge or by the heat of powder gases.

Safety Lug

An extra flange behind the bolt handle, at the rear of a bolt action receiver (notably the Mauser Model 1898), which uses the bolt handle as an extra locking surface in the extremely unlikely event of forward bolt lug failure.

Glock

The Glock pistol, sometimes referred to by the manufacturer as a Glock "Safe Action" Pistol, is a series of polymer-framed, short recoil operated, locked breech semi-automatic pistols designed and produced by Glock Ges.m.b.H., located in Deutsch-Wagram, Austria.

Brick

A box of ammunition roughly equal in size and weight to a brick. Most often used to describe a 500-round container of .22 Long Rifle ammunition.

Dud

A round of ammunition that does not fire.

Malfunction

A misfeed or other failure to fire which can be cleared on the spot and without tools.

Touch Hole

A small orifice at the breech end of the barrel of a muzzle-loading firearm through which the exploding priming charge is conducted from the flash pan to the main charge.

Upset Forging

A process that increases the diameter of a workpiece by compressing its length.

Holdopen Toplever

A catch built into the receiver of a break-open gun to keep the toplever in its extreme right position when the barrels are removed. This device makes it slightly easier to remount the barrels. As the barrels are mounted and the breech closed, the barrels contact some kind of release pin (marked with the arrow) and the toplever automatically returns to the center locked position. Because, however, it requires a separate act to find and to depress this tiny tab to re-center the toplever on a broken-down gun, this feature may be irritating when trying to put a gun away in its case.

Port

An opening. The ejection port is the opening in the side of a semi-auto from which spent cases are ejected.

Plus P

Also spelled "+P" or "P+". Is small arms ammunition that has been loaded to a higher internal pressure than standard for it's caliber. Many calibers are available in both standard and +p or +p+ variants. Ammunition marked +p produces more power and higher pressures than the standard ammunition. Not all firearms are designed to handle the increased pressure consult your owner's manual or gun manufacturer before using +P ammunition.

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