A firearm is formed by a housing, in which an assembly of a carriage and a barrel with a muzzle stop, and a breech are displaceably supported, and wherein the breech is equipped with a return spring that is supported on the rear support surface of the housing, has a counter weight displaceably disposed in a longitudinal space located between the housing and the carriage, on the support surface of which counter weight the rear end of the return spring is supported, and which is seated in the front position thereof on a front stop surface of the carriage. The breach is seated in the rear position thereof on a rear stop surface of the carriage, the return spring is also supported on a front support surface of the housing at the front end in the front position of the breech, and a transfer element protrudes into the path of the breech, the transfer element being simultaneously supported on the carriage and on the counter weight, and in the outer position thereof pushing the counter weight against a front stop surface of the carriage.