资料来源 : Webster's Revised Unabridged Dictionary (1913)

Breech action \Breech action\
   The breech mechanism in breech-loading small arms and certain
   special guns, as automatic and machine guns; -- used
   frequently in referring to the method by which the movable
   barrels of breech-loading shotguns are locked, unlocked, or
   rotated to loading position.