The Stoner 63, also known as the M63, XM22, XM23, XM207 or the Mk 23 Mod 0 machine gun, is an American modular weapons system designed by Eugene Stoner in the early 1960s. Cadillac Gage was the primary manufacturer of the Stoner 63 during its history. The Stoner 63 saw very limited combat use by United States forces during the Vietnam War, including the Navy SEALs and Marine Corps. A few were also sold to law enforcement agencies.