Abstract: A fuze of the type used in a rifle grenade assembly with a striker, a rotor nd a rotor lock includes one or more improvements. One pertains to the striker to prevent it from reaching a detonator-striking forward position more than once. Once it advances to the forward position it is locked in it by a spring biased locking pin. Other improvements relate to the release of the rotor by the rotor lock. The rotor remains locked, i.e. in the disarmed state even after intentional launching. It is released to assume the armed state only when the launched assembly accelerates at a certain rate toward the target.