Abstract: A typical embodiment of the invention has a gasket pressed between the flange on a hand grenade fuze and the bore in the grenade's firing mechanism body that exposes the percussion cap to the striker in order to make the fuze waterproof and dirtproof. A threaded ferrule bears against the flange to press the gasket into this engagement. A portion of the ferrule extends over a length of the fuze housing to provide a heat shield that establishes the burning time of the fuze. In this way, striker impact is enhanced through a rigid, although readily removable fuze mounting; attenuated fuze effects caused by fully waterproofed fuze lengths are avoided; and fuze assembly is completed after the striker is "cocked" and secured by the safety handle and associated cotter pin.