1. THE IMPROVEMENT IN SELF-LOADING GUNS WHICH COMPRISES A RECEIVER HAVING A BREECHBLOCK RECIPROCABLE THEREIN, A BEARING SURFACE ON THE BREECHBLOCK WHICH ENGAGES A SUPPORT SURFACE ON THE RECEIVER TO GUIDE THE BREECHBLOCK IN ITS REARWARD AND FORWARD TRAVEL, CLEARANCE FOR THE MOVEMENT OF THE REAR END OF THE BREECHBLOCK AT THE REARWARD END OF ITS TRAVEL, A DEFLECTOR SURFACE AT THE REAR OF THE RECEIVER, A DEFLECTOR SURFACE AT THE REAR END OF THE BREECHBLOCK WHICH ENGAGES THE DEFLECTOR SURFACE AT THE REAR END OF THE RECEIVER TO IMPART A TRANSVERSE THRUST TO THE REAR END OF THE BREECHBLOCK AND DECELERATE ITS REARWARD TRAVEL, AND MEANS ON THE BREECHBLOCK COACTING WITH MEANS ON THE RECEIVER TO MOVE THE REAR END OF THE BREECHBLOCK IN THE OPPOSITE DIRECTION AS IT MOVES FORWARD.