Glossary of firearms terms

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1 Distance across the bore measured from land to opposite land. In the U.S. and England this measurement is usually given in .00 or .000 of an inch. In Europe and Asia the measurement is generally expressed in millimetres. Commercial designation of a calibre need only be within several thousands of an inch of the true bore diameter.
2 In ballistics it is a unit expressing comparative dimensions, for example with a bullet if the length is three times the diameter it is described as three calibres long.

In mechanical terms, any inclined or eccentric surface imparting by sliding contact, a predetermined irregular motion to another part bearing upon it.

A breech lock carrying a firing pin and hinged at its forward end to permit opening the breech. Formerly used on certain breech loading rifles like the early Springfield.

Canister or case shot
A projectile consisting of a metallic cylinder filled with iron or lead slugs or ball of somewhat smaller diameter than those used in grape shot.

Circumferential, indented ring or groove around a cartridge case or bullet with a variety of uses. Serving to either hold sold lubricant of a lead bullet, or to receive metal stripped from the bullet in passing through the bore, or to prevent the bullet from being pushed too far into the case, or to crimp the case to the bullet.

Cannon lock
The most primitive form of hand gun ignition, achieved by the application of fire directly to the powder through a touchhole in the rear of the barrel.

In ammunition it is a small metal or paper device containing percussion ignited compound designed to explode the main charge.

Capucine see barrel band

1 A shortened rifle or musket, usually with a barrel length less than 22 inches and adapted for use by mounted troops.
2 In Europe, any short rifle. Historically the carbine (caraben, carabine) was introduced in England in the 16th century and was characterised by a bore smaller than a musket. In the 17th century it was a flintlock with a 30 inch barrel shooting balls of 24 to the pound. Subsequently it became a horsemanís gun, shorter and lighter than an infantry musket.

A small musketoon mounted on a swivel.

Cartouch or cartouche
1 A paper cartridge.
2 A cartridge box.
3 A gunners ammunition bag.
4 A wooden case filled with cannon balls.

Any of a variety of metal containers holding the complete charge of explosive, including primer powder and bullet. Formerly cartridge described powder contained in paper which was inserted into the chamber by pouring the charge through the muzzle. As such it dated from the end of the 16th century. Though paper cartridges contained no ignition component, they provided faster loading and better protection from dampness. Current metallic cartridges fall into several categories depending on the shape of the base and the type of ignition device.

Cartridge, ball
Any cartridge loaded with a single projectile is called a ball cartridge.

Cartridge, blank
A blank cartridge has no bullet, with a wad inserted instead to retain the powder.

Cartridge, bottle neck
Designates a cartridge where the powder chamber of which has a larger diameter than the bullet.

Cartridge, centre fire
Normally made of brass, aluminium or steel with the primer contained in a small metal cup in the centre of the cartridge base.

Cartridge, dummy
Designed for drill use and cannot be exploded. Such practice rounds are usually shaped and coloured differently to live ammunition.

Cartridge, guard
A cartridge containing a reduced charge, generally buckshot, for use in performing guard duty.

Cartridge, rim fire
Made of soft ductile metal, often copper, wherein the priming mixture is inserted in the rim at the head of the case and can be detonated by the blow from the hammer or firing pin at any point on the circumference of the rim.

Cartridge, rimless
Since a rim interferes with automatic feeding, either a rimless cartridge or a cartridge with a very small rim (semi-rim) is used in automatic weapons, a grip for the extractor being provided by a groove just above the base of the case. All rimless cartridges are of centre fire type.

Cartridge, rimmed
Characterised by a rim or flange around the base to prevent the cartridge from entering too deeply into the chamber, to sustain the blow of hammer or firing pin, and to provide grip for the extractor. Such cartridges may be either rim fire or centrefire.

Cartridge, semi-rimmed see Cartridge, rimless

Cartridge, signal
A cartridge containing vari-coloured luminous balls and used for signalling both on land and sea.

Cartridge clip see clip

The main body or container of a cartridge. Generally copper is used as the case metal for rim fire cartridges and brass is used for centre fire cartridges, steel and aluminium are also sometimes used. A bottleneck case has a diameter larger than the calibre of the arm, shaped like a bottle with the forward portion of the case necked down or reduced in diameter to hold the bullet. A ruptured case may describe a case from which the head has been ripped in discharge or more loosely a case split in firing so that gas has escaped.

Case shot
Small balls or bullets enclosed in a cylindrical case or canister.

Any mechanism used to secure any part in a desired position.

Centre fire cartridge see cartridge, centre fire

Chain shot
A projectile used both in shoulder arms and cannon from the 17th century to the 19th century, consisting of two balls joined by wire or chain. Not considered legitimate for use against men, chain shot was mainly used to tear enemy sails and rigging.

The enlarged rear end of the barrel that receives and supports the cartridge, aligning the bullet with the bore and the primer with the firing pin.

Chamber pressure see Pressure

Change lever
Device on an automatic weapon whereby the arm can be set on safe (non firing), automatic fire or semiautomatic fire.

1 In a cartridge case, the weight and type of powder.
2 In a primer, the weight and type of explosive.

Charger clip see clip

To ornament a surface of metal by cutting away parts, eg., embossing.

A French needle fire rifle introduced in 1866 and based on the German Dreyse gun.

Any longitudinal crack in wood, often caused in drying. Also called a gizzen or shake.

Checking, checkering
Roughing the stock or grip in a pattern of parallel or diagonal cross lines for ornamentation or improved gripping.

The bore of a shotgun barrel, the inside diameter of which is smaller at the muzzle than at the breech, designed to compress or constrict the load of shot in its travel through the barrel so that it leaves the muzzle in a more compact mass. A limit exists beyond which the mass cannot be compressed without deforming or smashing individual shot in the charge and thus causing a spotty shot pattern with large spaces where no shot has struck.

In ballistics, an instrument for determining velocity of a projectile between two points by measuring and recording the time required by the projectile to cover the distance between the two points.

Cleaning rod
Any rod used to clean the bore of a firearm.

Metallic cartridge holder to facilitate loading into repeating small arms. In the Mannlicher system a sheet metal box open at the top and bottom is filled with cartridges and inserted into the magazine well for direct feeding of cartridges from the clip into the chamber. As the last cartridge feeds into the chamber, the clip is automatically ejected from the weapon. In the Mauser system a metal spring, usually brass grips the rims of cartridges required to fill the weapons magazine. The clip is placed at the top of the magazine in guides to allow the cartridges to be stripped into the magazine by steady downward pressure of the fingers. Technically this cartridge holding device is a charger, though American usage designates it as a type of clip. Commonly in weapons with removable magazines, spare magazines into which cartridges are loaded manually are called clips, but this is improper use of the term. Revolver clips exist but are not often used, one example being the half moon clips used to fit .45 auto rimless rounds into .455 revolvers. Linked flexible clips have been devised for machine guns.

Clip guides
Machined slots to permit the insertion of the edges of cartridge clips or chargers for loading either in slides (military Steyr), in the receiver (U.S. Springfield), or in barrel extension Military Mauser).

1 On a flintlock weapon the hammer or piece holding the flint.
2 On percussion weapons, the piece striking the cap.
3 To draw back hammer or firing pin against mainspring compression in preparation for firing a weapon. At full cock the trigger mechanism engages the hammer or firing pin, holding it against mainspring tension, so that pressure on the trigger will release the hammer or firing pin, causing the mainspring to drive it against the primer to fire the weapon. Half cock arrangement on some firearms permits engaging the hammer in a notch far enough to the rear to prevent accidental firing of the primer. In this case trigger pressure will not fire the gun. In some revolvers half cock frees the cylinder to turn for loading and unloading.

Cocking piece
In certain small arms, the rear end of a long firing pin or striker, by which means the weapon may be manually cocked.

Cocking stud
Part of the cocking piece, a projection engaging the trigger or sear to hold the firing pin in the cocked position.

On an optical sight, to adjust line of sight to coincide with the axis of the barrel.

On a shoulder arm, the ridge at the upper forward part of the buttstock, used as a grip.

Compensator see Muzzle brake

On a percussion firearm, the tube on the end of which is placed the cap containing fulminate or other priming compound. When the hammer strikes the cap on the cone the resultant detonation sends a flash through the tube to ignite the charge. Also called a nipple.

Cone sight
A front sight of conical shape.

Plate or scroll of metal inlet into the stock of a gun opposite the lock. Though sometimes purely ornamental, it can also serve as a washer for the screws holding the lock in position. Also called a sideplate or nail plate.

A nitroglycerine propellant, so called because of the powders cord-like shape. Is was used principally in Great Britain.

Material, normally lead, contained within the bulletís outer metal jacket.

Rust and resultant pitting in a gun bore.

The dragging action of a trigger that delays immediate release of the hammer when correct pressure is applied. Any trigger movement after slack is taken up and before weapon is discharged.

On a cartridge case, the constriction at the mouth to retain the charge. Stab crimp is characterised by a succession of indentations around the case engaging the cannelure in the bullet jacket. Rolled crimp is formed by turning the case mouth inward to form a cannelure against the bullet around its entire circumference, thereby retaining the bullet at the proper seating depth. Both types of crimp are used on high pressure cartridges to retain the primer in the pocket.

Alloy used in the manufacture of small arm bullet jackets. Because of its tendency to deposit fouling in the bore, this alloy has been largely superseded by gilding metal.

A gun used in the 17th century, of the same bore as a caliver (a matchlock intermediate in size between a mousquet and a carbine), but with a longer barrel.

On modern rifles, a device to change fire from single shot to repeater and back again. Mounted on the receiver, it prevents cartridges from feeding out of the magazine. Thus those already held in the magazine are held in reserve while single cartridges are manually loaded into the chamber.

Cyclic rate
The rate, expressed in shots per minute, at which an automatic firearm can deliver uninterrupted fire.

On a revolving type firearm, the mechanism holding a number of cartridges and moving about an axis in such a manner that successive charges are correctly aligned and locked in position for firing.

Cylinder bore
On a shotgun barrel, when the bore diameter is constant from the breech to the muzzle.