A rifle comprising: - a housing assembly comprising an upper and a bottom housing portion, - a breech mechanism assembly arranged within the housing assembly and comprising • a bolt carrier assembly which further comprises a bolt carrier and a guiding sleeve fixed in the upper portion of the bolt carrier, • a bolt arranged in the bottom portion of the bolt carrier, • a guiding pin arranged through the central portion of the bolt carrier, and • a barrel receiver, - a rifle barrel screwed into the barrel receiver and comprising a gas adapter at the distal end of the rifle barrel, - and a self-loading mechanism comprising • a gas chamber with a guiding tube connected to the gas adapter, and • a piston assembly comprising an impact damper fixed within the housing assembly, a piston slidingly movable within the gas chamber, a guide fixed to the piston at one end and a return helical spring arranged around the guide in a way to lean against a stop in the guiding sleeve with one end and against the impact damper with the other end, characterized in that the guide is provided at its other end in the longitudinal direction of the guide with a blind hole, and the piston assembly further comprises a fixed piston slidingly movable at one end within the blind hole of the guide and fixed to the impact damper at the other end, a helical spring arranged within the blind hole of the guide in a way to lean against the bottom of the blind hole of the guide with one end and connected to the fixed piston with the other end, wherein the gas chamber is arranged on the rifle barrel in the area of the barrel receiver. - a housing assembly comprising an upper and a bottom housing portion, - a breech mechanism assembly arranged within the housing assembly and comprising • a bolt carrier assembly which further comprises a bolt carrier and a guiding sleeve fixed in the upper portion of the bolt carrier, • a bolt arranged in the bottom portion of the bolt carrier, • a guiding pin arranged through the central portion of the bolt carrier, and • a barrel receiver, • a bolt carrier assembly which further comprises a bolt carrier and a guiding sleeve fixed in the upper portion of the bolt carrier, • a bolt arranged in the bottom portion of the bolt carrier, • a guiding pin arranged through the central portion of the bolt carrier, and • a barrel receiver, - a rifle barrel screwed into the barrel receiver and comprising a gas adapter at the distal end of the rifle barrel, - and a self-loading mechanism comprising • a gas chamber with a guiding tube connected to the gas adapter, and • a piston assembly comprising an impact damper fixed within the housing assembly, a piston slidingly movable within the gas chamber, a guide fixed to the piston at one end and a return helical spring arranged around the guide in a way to lean against a stop in the guiding sleeve with one end and against the impact damper with the other end, characterized in that the guide is provided at its other end in the longitudinal direction of the guide with a blind hole, and the piston assembly further comprises a fixed piston slidingly movable at one end within the blind hole of the guide and fixed to the impact damper at the other end, a helical spring arranged within the blind hole of the guide in a way to lean against the bottom of the blind hole of the guide with one end and connected to the fixed piston with the other end, • a gas chamber with a guiding tube connected to the gas adapter, and • a piston assembly comprising an impact damper fixed within the housing assembly, a piston slidingly movable within the gas chamber, a guide fixed to the piston at one end and a return helical spring arranged around the guide in a way to lean against a stop in the guiding sleeve with one end and against the impact damper with the other end,