Barrel conversion kit for low recoil gun, especially for pistols and machine pistols

In a kit for changing the barrel of a gun, the barrel, breech, locking system, closing spring and striking pin are mounted in a specific housing part equipped with a sighting device and form with this housing part a firable constructional unit which is fastened rigidly, but releasably, in a predetermined relative position to the remaining gun having the grip piece and trigger system. On the housing part, a compensator or a housing extension can be fastened releasably in a predetermined relative position at its end corresponding to the barrel muzzle, the muzzle end of the barrel being mounted free of play in the compensator or in the housing extension.