The United States Navy and United States Coast Guard occupational rating of gunner's mate (GM) is a designation given by the Bureau of Naval Personnel (BUPERS) to enlisted sailors who either satisfactorily complete initial Gunner's Mate "A" school training, or who "strike" for the rating by showing competence in the field of ordnance. When "striking" one isn't required to be a seaman, but must belong to one of three undesignated rates: Fireman (FN), Seaman (SN), or Airman (AN). (Striking is no longer authorized in the USCG) It is also possible cross rate to Gunner's Mate. Cross rating refers to the act of an enlisted sailor "crossing" from their current rating to another rating of their choice, provided their ASVAB scores are high enough and there are open slots for the rate.