Chamber

Chamber, of a firearm, is the name given to that part of the bore which contains the powder, when its diameter is not the same as the Calibre (q.v.) of the gun. Formerly, chambers were always smaller in diameter than the bore, to prevent any air-space behind the projectile, but now that much heavier charges are fired, they are made larger. They tend to weaken the gun, but enable a shorter cartridge to be used, and so prevent the dangerous wave action which would be set up in a long one. See CANNON, RIFLED ARMS.