1. IN A LARGE CALIBER GUN HAVING A STATIONARY CARRIAGE SUPPORTING A RECOILING BREECH INCLUDING A VERTICALLY SLIDABLE BREECHBLOCK ADAPTED UPON THE UNLOCKING THEREOF TO DROP TO A FULLY OPEN POSITION, AND TORSION LEAF SPRING MEANS DEPENDING FROM THE BREECH FOR RETURNING THE BREECHBLOCK TO THE CLOSED POSITION THEREOF, THE IMPROVEMENT IN THE MEANS FOR WINDING AND UNWINDING THE TORSION LEAF SPRING MEANS, COMPRISING A ROTATABLE CRANK CONNECTED TO ONE END OF THE TORSION LEAF SPRING MEANS, A FOLLOWER PROJECTING LATERALLY FROM THE SIDE OF SAID CRANK, A CAM SURFACED FIXED TO THE STATIONARY CARRIAGE IN POSITION TO ENGAGE WITH SAID FOLLOWER DURING THE INITIAL RECOIL TRAVEL OF THE BREECH, A LATCH PIVOTALLY MOUNTED TO THE BREECH IN POSITION TO ENGAGE WITH SAID FOLLOWER AT THE CONCLUSION OF THE ROTATION IMPARTED TO SAID CRANK AND THEREBY PREVENT UNWINDING OF THE TORSION LEAF SPRING MEANS, MEANS FOR LOCKING THE BREECHBLOCK IN THE CLOSED POSITION THEREOF DURING THE ENTIRE RECOIL TRAVEL OF THE BREECH AND DURING THE COUNTERRECOIL TRAVEL THEREOF PRIOR TO THE PASSAGE OF SAID FOL-