Mark 23 or Mk.XXIII or variation, may refer to: U.S. Navy The U.S. Navy designation Mark 23 may refer to: Heckler & Koch Mark 23, a .45 ACP-caliber handgun Mark 23 machine gun, a configuration of the Stoner 63 weapons system used by US Navy SEALs. Mark 23 Pistol and Suppressor Kit, a Vietnam War-era kit issued to US Navy SEALs, containing a Mark 22 pistol and a Mark 3 noise suppressor. Mark 23 torpedo, a submarine-launched anti-ship torpedo used in World War II UK Royal Navy Mark 23 Grog, a British wire-guided 21-inch torpedo BL 6-inch Mk XXIII naval gun, a British WWII naval artillery gun QF 4-inch naval gun Mk XXIII, a British Cold-War submarine deck gun Other uses Bolo Mk XXIII, a fictional super-tank See also Mark 23 Mod 0