5 inch gun

The 5"/54 caliber Mark 16 gun (spoken "five-inch-fifty-four-caliber") was a late World War II–era naval gun mount used by the United States Navy, and later, the Japan Maritime Self-Defense Force. These guns, designed specifically for the Montana-class battleships, were to be the replacement for the 5"/38 caliber secondary gun batteries then in widespread use with the US Navy.