Caliber - A term that derives from Latin qua libra, meaning "what pound," first applied to the weight of a bullet and then to the diameter. Caliber now refers to the diameter of either a projectile or the bore of a gun. It is the approximate bore or groove diameter expressed (in English) in hundredths of an inch. A bullet that is 0.451" in diameter is 45 caliber. To write ".30 caliber" is technically incorrect. According to the strict definition, such a bullet would only be 0.003" in diameter! Frequently compounded with other descriptive words or numbers to create a cartridge name, e.g., 308 Winchester or 30-40 Krag. Also used in artillery as a measure of length equal to the diameter (or caliber) of a specified gun, as, a "fifty-four caliber" 5-inch naval rifle has a barrel that is 5x54", or 270 inches long. A "6 caliber" bullet ogive has a radius equal to 6 bullet diameters.


Canister Powder - A propellant powder intended for retail sale to hobby handloaders. As these hobbyists do not have access to pressure testing equipment and rely instead on published load data, every effort is made to insure that lot-to-lot variation over time is minimized. "Non-canister" propellants are sold in bulk to ammo manufacturers who have pressure testing equipment.


Cannelure - Circumferential groove(s) around a bullet or cartridge case. Used for identification, to hold lubricant, or for securing the bullet in the case..


Cap - See primer.


Cartridge - A complete unit of assembled ammunition: case, propellant powder, primer, and bullet. Commonly applied only to rifle and pistol ammunition, but technically correct for shotshells also.


Case - The paper, metal, or plastic container that holds all the other components of a cartridge. Sometimes called hull or shell.


Case Forming - To alter or modify one cartridge case to another of different shape and or caliber. Also see wildcat.


Case Hardening - A heat treating process which increases the surface hardness of iron alloys. Often produces distinctive colors, such as seen on the frames of Colt Single Action revolvers.


Case Trimming - Shortening an overly long case by removing metal at the case mouth.


Cast Bullet - Bullets for rifles or pistols cast from molten lead or lead alloy in a mould. See mould blocks


Center Fire (CF) - Refers to metallic cartridge case having a centrally located primer in the base. Also called centerfire. Most center fire cartridges are reloadable.


Chamber - That part of the barrel at the breech end, formed to accept and support the cartridge. In a revolver, chambers are located in the cylinder.


Chamber Cast - A casting, usually of sulfur or low melting-point metal, poured in the chamber to more easily measure chamber shape or condition.


Chamfer - To bevel or ream a taper on the inside of a case mouth to facilitate bullet seating.


Charge - The amount of propellant powder measured into the case in loading. Also refers to amount of shot measured into shotshell.


Choke - A constriction at the muzzle of a shotgun barrel designed to control the spread, or dispersion, of the shot charge.


Chronograph - An mechanical or electronic device used to measure the velocity of a projectile.


Collimator - In shooting, an optical device used to roughly align the sights with the bore of a rifle or handgun. Essentially, a collimator allows bore sighting without having to see through the barrel.


Combustion - Burning; in firearms, the chemical process which unites oxygen and other substances in gun powder to produce heat and gas. Also called deflagration.


Compensator - A device fitted to the muzzle of a firearm to reduce recoil or muzzle rotation. Usually applied to such devices when fitted to a handgun. See muzzle brake.


Components - The individual parts that go into the making of a cartridge.


Compressed Charge - A charge of powder which is compressed by the bullet during seating in the case.


Copper Crusher - Small, solid copper cylinder used in a pressure gun to measure chamber pressure. See pressure gun.


Cordite - Trade name for a long, tubular-grained, double-base powder used mainly in Great Britain, and one of the earliest smokeless propellants. The granules are often as long as the powder space.


Core - The interior part of a jacketed bullet; usually a lead alloy in sporting ammunition.


Corrosion - The eating away of the bore because of rusting or the chemical action of salts deposited in the bore by corrosive primers or powders. Cartridge cases can also be corroded by salts or acids.


Corrosive Primer - A primer whose burnt residue is hygroscopic (attracts moisture) and forms chemicals that can cause corrosion. These chemicals will rapidly rust a bore unless removed with a water-based solvent. All component primers in the U.S. have been non-corrosive for decades


Crimp - The bending inward of the mouth of the case in order to grip the bullet, or to close the mouth of a shotshell case. Two types are used. A roll crimp is the bending or rolling the mouth of the case into the crimp groove or cannelure of the bullet. In a taper crimp, the mouth of the case is pressed into the bullet body without bending the case mouth.


Crimped Primer - A forcing inward of the brass around the top of the primer pocket to prevent set-back of primers. This is usually found on military cartridges intended for use in fully automatic weapons. Unless the crimp is removed after depriming—either by swaging or reaming—repriming of the case is very difficult.


Cupro-Nickel - A copper-nickel alloy once used extensively for bullet jackets. It was largely replaced by gilding metal because of barrel fouling problems.