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


Single Shot

A firearm that is only capable of holding one shot at a time. Each round must be loaded into the chamber manually by hand before each shot.

Sectional Density

The relationship between a bullet's weight and its diameter. A long bullet, such as the original 7.62x54R loading for the Mosin Nagant 91/30, will have a high sectional density and consequently greater penetration than a shorter bullet of similar construction. A shorter bullet with less sectional density will have relatively less penetration, but greater knockdown power.

Factory Ammo

Ammunition that has been assembled by a commercial vendor of ammunition and sold in retail stores. This is as opposed to Hand loads which have been assembled by individuals and are not typically sold.

Turn-Bolt Action

A bolt action which is locked by pressing the bolt handle in and down, thereby turning its locking lugs into the receiver.

Lede

The bevelled portion of the rifling at the rear end of the barrel (and the forward portion of the chamber) where the bullet first engages the lands.

Double-Set Trigger

Usually only found on black powder muzzle loading rifles and pistols, pulling the rear (set) trigger converts the front (main) trigger to a light, hair trigger (too light and sensitive to be carried safely in the field). While the front trigger is always at the ready, if one has the time, using the set trigger feature may allow for a more accurate long-distance shot. Operates using its own miniature firing mechanism (sear, spring and hammer) when cocked, to multiply the force of a pull on the main trigger.

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.

Primer Ring

Refers to a visible dark ring created by the primers in centerfire ammunition around the firing pin hole in the frame after much use.

WSM

Abbreviation for Winchester Short Magnum.

Moon Clip

A moon clip is a ring-shaped or star-shaped piece of metal designed to hold multiple cartridges together as a unit, for simultaneous insertion and extraction from a revolver cylinder. Unlike a speedloader, a moon clip remains in place during firing, and after firing, is used to extract the empty cartridge cases.

Feed

The action of moving live cartridges from the magazine of a firearm into the chamber.

Stripper Clip

Simple clips made of metal or sometimes plastic that hold several rounds of ammunition in a row and is used to quickly fill a magazine.

Windage

The setting on the sights used to accommodate the wind or adjust for horizontal (side-to-side) errors in the alignment of the sights with the bore of the firearm.

Monoblock Barrels

A method of building a pair of barrels where the entire breech end of both barrels and the lumps together are machined from one solid piece of steel. The barrel tubes are then fitted separately into this monoblock and the ribs attached. Often identifiable by a distinctive ring around the barrels about three inches in front of the breech end. The favored jointing method of the Beretta company. An incorrect euphemism for sleeved barrels.

Parallax

This occurs in telescopic sights when the primary image of the objective lens does not coincide with the reticle.Telescopic sights often have parallax adjustments to minimize this effect.

Throat Erosion

The wearing of the portion of the barrel where the gas pressure and heat is highest as the projectile leaves the chamber. The greater the chamber pressure the more rapid throat erosion occurs which is compounded by rapid firing which heats and weakens the steel.

Gas Port

A small hole in the barrel of a gas-operated firearm through which expanding gases escape to power the autoloading system.

Bandolier

A pocketed belt for holding ammunition and cartridges. It was usually slung over the chest. Bandoliers are now rare because most military arms use magazines which are not well-suited to being stored in such a manner. They are, however, still commonly used with shotguns, as individual 12 gauge shells can easily be stored in traditionally designed bandoliers.

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.