Automatic weapon

The invention relates to firearms, in particular to designs of automatic small arms. 5.45 mm Kalashnikov assault rifle is known (see V. I. Murakhovsky, E. A. Slutskly. "Special Purpose Weapons" Moscow 1995 p.44). An automatic weapon has a housing with a movable spring-mounted barrel assembly having a barrel and a receiver . The receiver has a spring-mounted bolt support with a bolt , a buffer mechanism and a firing pin mechanism having a movable firing hammer which interacts with the bolt support . The housing has a trigger mechanism with a firing trigger , a sear with a spring-mounted pawl interacting with the trigger and the firing hammer , and a movable tripper with cams () interacting with the spring-mounted pawl and the trigger . A device angularly displaces the barrel assembly relative to the housing and a muzzle attachment device has expanding chambers with intercrossing cavities.