Abstract: A key actuated safety mechanism is described for mounting in the hand grip of a revolver or other hand gun. The safety mechanism includes a rotary operator having an eccentric projection which upon rotation to a locked portion directly engages the hand gun firing mechanism as a stop to prevent firing, or is coupled to such firing mechanism by a lock bar which acts as the stop. An improved key actuated rotary lock for use with such safety mechanism is also described having a cam actuated, spring biased plunger operated by the key inserted into an opening through such plunger for enabling the lock to be rotated between locked and unlocked positions.