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


Eye Dominance

Although we have two eyes for depth perception and for spare parts, there is a natural tendency for one eye (the master eye) to take precedence over the other, regardless of the relative visual acuity of each eye. It is a fortunate condition when the eye on the side of the shoulder where one is comfortable mounting a gun is also the dominant eye.
To test for eye dominance:

Pick out a small object several feet away. With both eyes open, center your right index finger vertically over the object. Close your right eye. If your finger appears to jump to the right, you are right eye dominant. Then open your right eye and close your left eye. If your finger remains in position in front of the object, you have confirmed your right eye dominance. Alternatively, if in the above test, upon closing your right eye your finger remains in position covering the object, you are left eye dominant. If you close your left eye instead and your finger appears to jump to the left you have confirmed your left eye dominance.
Eye dominance problems can be treated with
1. A severely-cast, crossover stock to bring the dominant eye in line with the gun's line of sight, 2. A patch over the dominant eye, or just a small piece of frosty Scotch tape on shooting glasses intercepting the dominant eye's line of sight, 3. Fully or partially closing the dominant eye, or 4. Learning to shoot from the dominant-eye shoulder.
While less convenient, methods that retain the use of both eyes better preserve the ability to perceive depth in three-dimensional space, a great benefit in wingshooting.

Trap

A game of competitive clay pigeon shooting on a formally designed layout. In plan view, one launching machine is located 16 yards in front of a straight line, firing rising targets perpendicular to and away from that line. Five competitors shoot five individual targets at each of five stations along that line. Although each target is presented at slightly randomized vectors, trap emphasizes generally a single type of shot, outgoing and rising, and targets are broken at generally longer ranges than Skeet.

Slide

The upper portion of a semi-automatic pistol that houses the barrel and contains the breechblock and portions of the firing mechanism. Ejecting the spent case as it moves to the rear and loading a fresh cartridge into the chamber as it moves forward again. As its name states, it slides along tracks in the top of the frame during the recoil process providing the linkage between the breechblock and barrel.

Recoil Spring

The recoil spring is the powerful spring that cushions the slide in its rearward travel and then sends the slide forward again with enough force to drive the fresh round firmly into the chamber. The strength of the recoil spring is calibrated to run the slide without any outside assistance.

Magazine Disconnect

Another term for Magazine Safety

Heel & Toe Plates

Protective plates, usually of steel or horn, covering the top and bottom of a gunstock's butt only (the heel and the toe); leaving wood exposed in the center

Picatinny Rail

A metal bar, available in a variety of lengths, with a continuous row of Weaver-like scope mount base slots, which when attached to a firearm, allow convenient attachment of a variety of sights, lights, slings, bipods and other accessories designed to fit this standard system.

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