1. A LAUNCHER ATTACHABLE TO A FIREARM BARREL FOR SUCCESSIVELY AND SEMIAUTOMATICALLY DISCHARGING A PLURALITY OF ROUNDS EACH INCLUDING A GRENADE AND A PROPELLANT INCLOSING CASE, THE LAUNCHER INCLUDING A FIRING TUBE DISPOSED FOR RECIPROCATION BETWEEN A FORWARD ROUND LOADING POSITION AND A REARWARD BATTERY POSITION WHEREIN THE LOADED ONE OF SAID ROUNDS IS INCLOSED BY SAID FIRING TUBE FOR DISCHARGE, A SPRING FOR BIASING SAID FIRING TUBE FROM THE LOADING TO THE BATTERY POSITION, RIFLING FORMED IN SAID FIRING TUBE, A ROTATING BAND FORMED ON EACH OF SAID GRENADES SO AS TO BE ENGRAVED BY SAID RIFLING DURING PASSAGE OF SAID GRENADE UPON DISCHARGE FROM THE CASE ALONG SAID FIRING TUBE TO FRICTIONALLY TRANSFER ENERGY FROM THE DISCHARGE GRENAGE TO SAID FIRING TUBE FOR ACTUATION THEREOF TO THE LOADING POSITION, AND ADDITIONAL SHORT SECTIONS OF RIFLING PROVIDED AT THE MUZZLE END OF SAID FIRING TUBE TO INCREASE THE ENERGY FRICTIONALLY TRANSFERRED TO SAID FIRING TUBE.