Letter: B

A leakage of propellant gas forward past the bullet in the barrel.

A self-loading action in which the breech block is stationary and the barrel moves forward to cycle the action.

A pellet distribution (pattern) with an unusually low percentage of pellets and/or of erratic distribution. Depending on its overall shape and pattern distribution, may also be referred to as a Doughnut Pattern.

A primer that is separated completely from the cartridge or shotshell after firing due to severe expansion of the primer pocket and head.

The opening or clearance between barrel and cylinder in a revolver. See also Cylinder Gap.

The combination of barrel and receiver or frame together with the other parts of the mechanism by which a firearm is loaded, fired and unloaded.

A cylindrical component that is assembled into the head end of a shotshell.

The condition where the breech of the action is in proper position for firing.

A component of a shotshell primer; a flanged metallic cup that contains and supports the primer cup and anvil.

1. A flanged metal cup having a flash hole at the bottom end. 2. An ignition component using a battery cup as a holder for the other elements, usually found in shotshells.