compression spring 52 and comes to rest on the supporting surface 90 assuming proper operation the above described sequence is repeated as long as the fire initiating device which will not be discussed in detail here is actuated and firing occurs in the case of misfiring and again under consideration of fig1 and 3 there results the above described sequence with the difference that no shot is fired when point s passes through the extension of axis a 3 consequently no volume of propellant gas is produced which could deflect the control piston 54 toward the left the stop abutment 88 abuts on the free end 58 of the control piston 54 which projects into its circular path of movement this results in the rotary movement of the control roller 84 being blocked and for safety 39 s sake the breech block remaining closed even if firing is delayed it must be assured that the breech block remains closed at least during the time of passage of the projectile this is done as follows due to the delayed firing the stop abutment 88 abuts against the free end 58 of the control piston 54 while the breech block is still closed the control roller 84 is stopped when the shot is fired with a delay the control piston 54 is driven to the left the control roller 84 moves on again and before it reaches its zero position shown in dot dash lines given by the angular path associated with the period of passage of the projectile and the subsequent releasing and opening of the breech block the projectile has.