Abstract: An automatic weapon has a housing 1 with a movable spring-mounted barrel assembly 6 having a barrel 7 and a receiver 8. The receiver 8 has a spring-mounted bolt support 24 with a bolt 27, a buffer mechanism 32 and a firing pin mechanism 33 having a movable firing hammer 36 which interacts with the bolt support 24. The housing 1 has a trigger mechanism 50 with a firing trigger 52, a sear 43 with a spring-mounted pawl 18 interacting with the trigger 52 and the firing hammer 36, and a movable tripper 53 with cams (56, 67) interacting with the spring-mounted pawl 48 and the trigger 52. A device angularly displaces the barrel assembly 6 relative to the housing 1 and a muzzle attachment device 13 has expanding chambers with intercrossing cavities.