Abstract: An actuation mechanism for an automatic firing weapon, the barrel of which can be connected through the agency of a gas removal channel with a compartment of a cylinder, an actuation piston for the cylinder by means of which there can be maintained open the connection of the compartment with the barrel in a starting position of the actuation piston. The actuation piston can be displaced into a rearward position in the cylinder by means of the gases tapped-off via the gas removal channel, and the compartment during the forward movement of the actuation piston can be closed by such actuation piston prior to reaching the starting position for the purpose of damping the piston movement. The compartment filled with gases is closed in the rearmost position of the actuation piston.