Letter I Firearms Glossary

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Improved Cartridge

A wildcat cartridge that is created by straightening out the sides of an existing case and making a sharper shoulder to maximize powder space. Frequently the neck length and shoulder position are altered as well. The caliber is NOT changed in the process.

Improvised Firearm

A firearm manufactured by someone who is not a regular maker of firearms.

Inertia Firing Pin

A firing pin which moves freely forward and backward in the breechblock.

Inletting

The process of carving out recesses in wooden stocks with precision, using gouges, chisels and scrapers to accept the steel components of a firearm.

Integral Lock

A built in lock that may prevent the firearm from being fired.

Intercepting Sear

A second sear, poised just behind a second notch in the hammer. It is possible that when a cocked firearm is dropped or sharply jarred, a single sear could jump out of its notch and the hammer could fall, firing the gun accidentally. In this event, an intercepting sear would engage before the hammer could fall completely, preventing an accidental discharge. On a gun with intercepting sears, only by pulling the trigger are both sears moved out of the way simultaneously, allowing the gun to fire. Intercepting sears are usually found on better sidelock actions. They are sometimes found on best boxlocks, and can be recognized by an extra screw behind the action fences, in addition to the usual two screws (or pins) along the lower rear of the receiver.

Internal Safety

A safety which is placed within the gun and is not accessible to the user. Internal safeties are generally designed to prevent unintentional discharges when the gun is dropped or mishandled.

Internal Trigger Lock

A internal locking device built into a firearm, usually operated with a key, to render it unable to be fired. A good example of a internal trigger lock are the ones found on the semi-automatic pistols manufactured by Bersa.

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.

Iron Sights

The mechanical sighting system which usually comes with the firearm made of metal with no optics.

Island Rear Sight

A rear barrel sight base, more articulated than having the sight simply dovetailed into the barrel, but not requiring as much gunsmithing as having it mounted onto a proper quarter-rib.

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.


7 Other Firearms Definitions You Need To Know


Magazine

A secure storage place for ammunition or explosives. On a firearm, it is the container, either fixed to a firearms's frame or detachable, which holds cartridges waiting to be fed into the gun's chamber.
Detachable magazines for the same gun may be offered by the gun's manufacturer or other manufacturers with various capacities. A gun with a five-shot detachable magazine, for instance, may be fitted with a magazine holding 10, 20, or 50 or more rounds.
Box magazines are most commonly located under the receiver with the cartridges stacked vertically.
Tube or tubular magazines run through the stock or under the barrel with the cartridges lying horizontally (like on a shotgun or lever action rifle.
Drum magazines hold their cartridges in a circular mode (for example the famous drum magazine on a Thompson submachine gun).
On a revolver, the magazine is known as the cylinder.
Internal magazines are built into the firearm and are not removable. Examples of internal magazines are the tube magazines of a shotgun or the magazine on a Mosin Nagant.
A magazine is not a clip!

Double Action

An action type that when the trigger of a gun is pulled, the gun gets cocked and the hammer (or striker) is dropped. This applies to both revolvers and semi-automatic guns. On a double action revolver, when the trigger is pulled, the hammer is cocked before releasing. With a double-action semi-automatic pistol, the hammer does not have to be manually cocked (via actually pulling back the trigger or tracking the slide), the hammer (or striker) will be cocked while the trigger is being pulled. A firearm that only the hammer drops when the trigger is pulled is a single action gun.

Yaw

The heading of a bullet, used in external ballistics that refers to how the Magnus effect causes bullets to move out of a straight line based on their spin.

Lock

The firing mechanism of a a muzzle-loading weapon. In breech-loading firearms, the lock is the firing mechanism and breech-sealing assembly.

C&R

Abbreviation for Curio and Relic

Live Fire Exercise

Any exercise in which a realistic scenario for the use of specific equipment is simulated. In the popular lexicon this is applied primarily to tests of weapons or weapon systems that are associated with the various branches of a nation's armed forces, although the term can be applied to the civilian arena as well.

Failure To Feed

A semi-automatic firearm malfunction in which the slide passes entirely over the fresh round, failing to pick it up to insert into the chamber as the slide returns to battery.