Abstract: The invention relates to a gun provided with recoil brake (14) and a method for improving the efficiency of the same. During the method a portion of the gunpowder gases burnt by means of the oxidant present in the barrel (2) of the gun but still containing inflammable material is introduced as the primary medium from the barrel (2) of the gun into the nozzle (9) of an ejector and the secondary medium is thus pumped in for forming a pre-mixture which is introduced into the combustion chamber of a pulsating reactive drive mechanism (10) acting in a direction opposite to the direction of the shot. This mixture is further burnt by means of the medium containing oxidant present in the drive mechanism (10), the combustion product is led out through the blow pipe (18) and the flow-back taking place during combustion is avoided by means of a valve.