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


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.

Stance

How the shooter positions her body while shooting. The three most widely used handgun stances are Weaver, Isosceles and Chapman stance.

DST

Abbreviation for Double-Set Trigger

Grooves

The cut-away, concave portions of the rifling inside the barrel of a firearm discharging a single projectile.In other words, the lower portion of rifling.

Recoil Lug

A stout flange, invariably incorporated into the underside of the front receiver ring of a bolt action, and also frequently incorporated into the underside of the barrel of a heavily-recoiling rifle, which when properly bedded, transfers recoil to the stock.

Minute Of Angle

A 1/60th part of a degree, the unit of measure used in adjusting rifle sights. As it turns out conveniently, a minute of angle translates almost exactly to one inch at 100 yards (actually 1.047 inches), to two inches at 200 yards and three inches at 300 yards

Cover Hold

Sometimes also known as cover-up hold. A sight picture of when the center of the target is completely covered by the front sight when the sights are properly aligned. Also see center hold and six o'clock hold.

Zero

A firearm is said to be "zeroed in" when its sights have been adjusted so that the bullet will hit the center of the target when the sights are properly aligned upon the center of the target. The farthest distance from a firearm at which the bullet's path and the point of aim coincide. This term is also used to mean the process of insuring that the sights of a firearm are properly aligned so that where they indicate the bullet will strike is in fact where it strikes.

Combination Gun

A shoulder-held firearm that has two barrels; one rifle barrel and one shotgun barrel. Most combination guns are of an over/under design (abbreviated as O/U), in which the two barrels are stacked vertically on top of each other, but some combination guns are of a side-by-side design (abbreviated as SxS), in which the two barrels sit beside each other.

Isosceles Stance

There are two basic variants of the Isosceles stance, the Traditional Isosceles and Modern Isosceles stance. In both Isosceles stances, the feet parallel pointing toward the target and are roughly shoulder width apart. Both arms are stretched almost equally forward with the gun centered forward, creating the triangular shape which gives the stance its name.

Checkered Butt

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

Bolt Thrust

The amount of rearward force exerted by the propellant gases on the bolt or breech of a firearm action or breech when a projectile is fired. The applied force has both magnitude and direction, making it a vector quantity.

Locking Lugs

A series of projections on the bolt of a firearm designed to fit into corresponding slots in the receiver to lock the action in closed position for firing.

Single Action

An action type that when the trigger is pulled, the only thing the trigger does is drop the hammer (or striker). This applies to both revolvers, semi-automatic and automatic guns. On a single action revolver, the gun must be manually cocked before it can be fired. With semi-automatic and automatic guns that are single action, the only thing the trigger does is drop the hammer, striker or firing pin onto the cartridge. Then the firearm is cocked again when from the recoil of the fired round. A firearm that the gun is cocked and the hammer drops when the trigger is pulled is a double action gun.

Globe Sight

A front sight assembly, primarily for target rifles, consisting of a tube, housing interchangeable beads and blades. The tube guards against imperfect aiming due to sight pictures influenced by reflections.

Short Recoil

A semi-automatic pistol in which the barrel and breechblock are locked together for only a short distance of rearward recoil travel, at which point the two are uncoupled, the barrel is stopped and the breechblock continues rearward, extracting the spent casing from the chamber. Upon returning forward, the breechblock chambers a fresh round and forces the barrel back into its forward position. Most modern recoil operated semi-automatic pistols use short recoil.

Pair

Two shots fired very quickly with the use of the sights.

Squib

An underpowered powder charge, usually caused by a fault in cartridge loading, often insufficient to expel a projectile from the muzzle of a firearm. If such a blockage is not cleared, the next attempted shot could cause the barrel at least to bulge, and very possibly to burst.

Short Trigger

A trigger that doesn't have to travel very far before it reaches the break. In a 1911 semi-auto pistol, a short trigger is a different part than a long trigger, and (in addition to providing less motion) it features a shorter reach which may be of benefit to a small-handed shooter.