1. IN A BREECHLESS, RECOILLESS WEAPON HAVING A PROJECTILE PROVIDED WITH A VENTURI NOZZLE SECURED TO AN END OF SAID PROJECTILE, A PROPELLANT CHARGE CARRIED BY SAID PROJECTILE AND MEANS FOR IGNITING SAID PROPELLANT TO FIRE SAID WEAPON AND PROJECTILE, THE COMBINATION THEREWITH OF THE IMPROVEMENT ENABLING SAID NOZZLE TO BE RELEASED BY PRESSURE OF SAID PROPELLANT AND YET HELD BY SAID GUN UNTIL AFTER SAID PROJECTILE HAS BEEN RELEASED FROM SAID NOZLE, SAID IMPROVEMENT INCUDING SAID NOZZLE BEING OF A THIN EXPANSIBLE METAL PROVIDED WITH A SHALLOW BUT SECURE FLANGE, GROOVE MEANS AT A FORWARD PORTION OF SAID NOZZLE FOR HOLDING THE SAME ATTACHED TO SAID PROJECTILE, SAID WEAPON PROVIDED WITH AN INTERNAL GROOVE SUBSTANTIALLY RADIALLY ALIGNED WITH SAID FLANGE, AND SAID FLANGE BEING OF A SIZE OF ENGAGEMENT IN SAID WEAPON GROOVE, A FORWARD WALL OF SAID WEAPON GROOVE EXTENDING RADIALLY INWARD