Glossary of firearms terms

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Backlash
1 Superfluous motion in linked mechanical parts.
2 Rearward travel of the trigger beyond the point where the hammer or firing pin is released to discharge the weapon.
3 Failure of sight adjusting screws to move the sight positively the proper distance for each rotation of the adjusting screw.

Back strap
Metallic strip along the back of a pistol or revolver grip.

Ball
1 A round lead or iron object discharged by a smooth bore firearm.
2 Any spherical projectile larger than a small shot.

Ball cartridge
In small arms, any cartridge containing a single projectile regardless of shape, and a propelling charge.

Ballistics
Science of the performance of projectiles, relating to their trajectory, energy, velocity, range, penetration, etc. Exterior ballistics are concerned with the flight of a bullet after leaving the muzzle of a gun. Interior ballistics are concerned with the explosion of the primer, ignition and burning of the propellant powder, internal pressures and torques resulting as the bullet is forced through the barrel.

Barrel
Metal tube designed to contain the exploding charge in the breech and concentrate the force of the gases generated by the explosion in a manner that provides initial velocity and proper direction to the projectile being discharged.

Barrel band
Strip of metal encircling and fastening together the stock and the barrel. Also called a capucine.

Barrel extension
Frame into which a machinegun barrel is screwed, serving as a mount for various parts of the weapon’s action.

Barrel, subcalibre see Adapter

Bar shot
Projectile consisting of two cannon balls or half balls joined by a bar of iron.

Battery see Frizzen

Battery cup
A pocket in the head of a centre fire cartridge case where the primer is placed.

Bell-mouthed
Flaring at the muzzle to scatter shot, as in a blunderbuss.

Berdan primer see Anvil

Bipod
Any two legged support, normally for the muzzle of a gun.

Black powder see Powder

Blade
A type of upright, elongated front sight.

Blank cartridge see cartridge

Blending
The act of mixing powders of the same or different lots to yield charges of uniform ballistic characteristics.

Blowback
1 The normal reaction of powder gasses directly rearward against the bolt or breechblock at the time of explosion and sometimes used to operate the action.
2 Rearward escape of powder or primer gasses from the chamber around the bolt or breechblock caused by a split or fractured cartridge case or a punctured primer.

Blowback action see Action, blowback

Blown primer
A primer blown loose from its seat in the battery cup by the action of powder or primer gasses.

Blueing
The process of artificial rusting to colour metallic parts various shades of blue or black.

Blunderbuss
Smoothbore firearm with a bell mouthed muzzle and of large calibre, introduced into England in the late 16th century, probably from the Netherlands. Muzzles were either round or oval shaped and were designed to scatter the charge when fired. Not generally used for military weapons, blunderbusses were carried for protection against thieves and as such were used as late as 1840.

Bolt
The part of the action that locks the mechanism during discharge. In bolt action weapons it is the cylindrical or oblong block of steel so designed that it may be pushed forward and locked to seal the breech for firing, then withdrawn to permit ejection of the fired case and loading of another cartridge.

Bolt action see Action, bolt

Bolt cylinder
1 The rear cylindrical portion of a two piece bolt into which the bolt head slides, and to which the bolt handle is fixed.
2 The main body of a one piece bolt, carrying the locking lugs and bolt handle. It encloses the striker and main spring.

Bolt face
The forward end of the bolt against which the base of the chambered cartridge rests.

Bolt sleeve
The part of the bolt assembly that fits into or over the bolt cylinder. The firing pin or striker passes from the bolt cylinder through the bolt sleeve to be anchored in the cocking piece.

Bolt stop
A projecting metal spur to halt the rearward travel of the bolt.

Bombardelle
One of the earliest forms of hand gun (c.1380), characterised by a short barrel loaded through the muzzle and a short straight rod longitudinal to the bore. A touchhole atop the rear of the barrel provided a means of ignition.

Boot
Scabbard attached to a saddle to receive a rifle or carbine.

Bore
The hole extending longitudinally through the gun barrel from chamber to muzzle. Formerly bore size designated a measurement of bore diameter in terms of the number of spherical bullets that fitted the barrel totalling one pound in weight.

Bore diameter
In a rifled arm, the diameter of the bore before rifling, the diameter measured from the top of one land to the top of the opposite land.

Bore sighting
The process of aligning sights with the bore axis by sighting through the gun bore at a target, holding the gun rigid and adjusting the sights to make the line of sight parallel to the bore.

Bottleneck see Case, cartridge

Bound
That segment of a trajectory occurring between two grazes.

Bourrelet
The finished portion of a projectile immediately behind the ogive, larger than the remainder of the body and serving to centre the projectile in the bore of the bore.

Boxer primer see Anvil

Breech
The rear face of the barrel and more loosely, the related mechanism of the chamber and receiver.

Breechblock
That part of the action which, being locked into position, supports the cartridge in the chamber of the gun, so that the case may form an effective gas seal when the weapon is discharged. Although a bolt is a breechblock it is not normally so called.

Breechloader
Any firearm loaded through the rear of the barrel, including all modern powder weapons.

Breech lock
The mechanism that closes the rear of the bore against the forces of discharge.

Breech plug
In muzzle loading weapons, a cylindrical plug screwed in at the breech to close the bore.

Bridle
In mechanical terms, a strip of metal joining parts or restraining their movement. Used to reinforce the lock of some firearms, it is positioned between the pan and the frizzen’s pivot point.

Broad arrow
Symbol or identifying mark that signifies ownership or control by the British Crown.

Brown Bess
English flintlock musket used extensively in the European wars from the late 17th century to the end of the 18th century, including the American Revolution. It weighed approximately eleven and a half pounds and fired an inch and a half ball a distance of 125 yards.

Browning
Chemical process for colouring the metallic parts of a firearm for protection against atmospheric action and also to reduce light reflection. Often the term is used incorrectly to denote bluing.

Brown powder
Gunpowder made with unburnt charcoal.

Buck horn sight
A type of rear sight which derives its name from the deeply curved form of its notch.

Buffer
Any part intended to absorb shock or check recoil.

Bullet
The projectile discharged by a firearm. A so called lead bullet is composed of lead mixed with one or more hardening ingredients.

Bullet, armour piercing
Contains a hard metal core so supported by the jacket and metal envelope so that armour will stop movement of the latter while allowing the core to continue forward for penetration.

Bullet, dumdum
A dumdum is a generally misused and outmoded term, first applied unofficially to open point bullets made at the British arsenal at Dumdum, India. It gradually came to apply to any expanding point bullet, however none of the current expanding point bullets are properly called dumdum.

Bullet, full metal patch
A bullet designed with a metal case covering the nose and crimped over the core at the base is called a full metal patch (FMP) bullet.

Bullet, hollow point
A bullet with a nose cavity designed to increase expansion on impact, is now generally obsolete except in .22 rim fire cartridges.

Bullet, incendiary
A bullet containing an incendiary mixture or compound generates intense heat on impact.

Bullet, jacketed
A bullet with gilding metal, soft steel, cupronickel, or other metal envelope covering a lead or steel core. A steel jacketed bullet has a soft steel jacket and is often flash coated or plated to minimise bore resistance and prevent rusting.

Bullet, metal patched
Loosely means any metal jacketed bullet. More precisely it refers to a bullet with a metal cup covering its base and extending forward over that portion of the bullet that comes in contact with the rifling. The lead core at the nose of the bullet remains exposed. The term originated when thin metal was first substituted for parchment patches formerly used on lead bullets to protect the base from the heat of early heavy charges. Any bullet designed to expand on impact is commonly called a mushroom bullet, though technically the term applies to a metal patch bullet with an exposed rounded nose and suitable for use only in weapons of relatively low velocity.

Bullet, tracer
A bullet containing, inside the jacket at the base of the bullet, a substance ignited on firing to show a brilliant light during its flight. It has an incendiary effect if flight is interrupted by impact before the light is exhausted.

Bullet, wad cutter
A bullet with a square shoulder at or near its nose for making a clean round hole in paper targets.

Bullet ramp
The inclined surface at the entrance to the chamber which guides the cartridge into position for firing.

Bullet shell
For small arms, an explosive bullet.

Bullet splash
Metal particles sprayed from a bullet on its impact against armour or other hard material.

Bullseye
The centre of a target.

Burr hammer
An exposed hammer with a serrated knob that allows a gripping surface for manual cocking.

Bushing
Any removable metal lining, generally a thin metal ring surrounding a part to provide either a bearing surface or a tighter fit than direct machining could achieve.

Butt
1 Embankment or parapet on a target range to stop the flight of bullets behind the target.
2 The rearmost face of the stock on a shoulder arm.
3 The bottom of the grip on a handgun.

Buttcap
The metal cap covering and protecting the butt on a handgun.

Buttplate
The metal or composite plate used to cover, protect and reinforce the butt on a shoulder arm.

Buttstock
Portion of the stock extending from the receiver to the butt on a small arm.