 Eliminating water cooling saved a great deal of weight, but the water jacket was a crucial component of the gun, as it held the bushing which supported the muzzle end of the barrel and allowed it to recoil.Thus, the water jacket structure was retained, but was heavily perforated to allow cooling air-flow to reach the barrel, leaving more open space than metal.This much-lightened structure, resulting from just over 50% of the jacket's circumferential sheetmetal removed for its cooling slots; was strong enough to support the barrel, but not enough to handle the powerful forward counter-force created when the expanding gases in a muzzle brake forced the barrel rearwards.