Abstract: The disclosure relates to an automatic gun which employs case ejectors (1, 1') for realizing extraction and ejection of the cartridge case from a spent round. The case ejector is also utilized for arresting the breech block during the recoil of the weapon and holding the breech block in an open position so that ramming home of a new round (3') may be executed. The ejector is exposed to the round in process of being rammed home, which round, during its thrust towards the homed position in the barrel, entrains the ejector so that the breech block (2) is released and may execute its closing movement int. al. with the assistance of spring means placed under tension during the opening movement of the breech block. The ejector and the breech block are designed with cooperating arrest and abutment surfaces which take up portions of the kinetic energy of the round which is in the process of being rammed.