The Mark 2 quadruple mounted 40 millimeter gun mount, or Quad 40, was a primary antiaircraft weapon used by Allied forces during the violent air and sea battles of World War II. Each Quad 40 gun could fire two-pound shells at a sustained rate of 160 rounds per minute, reaching ranges of more than five nautical miles and nearly four nautical miles in altitude. Weighing 24,900 pounds per mount, these weapons equipped battleship Wisconsin in great numbers, with twenty emplacements carrying a total of eighty 40 millimeter gun barrels. U.S. Navy battleships such as Wisconsin served mainly as heavily armored refueling and antiaircraft platforms supporting the fast-carrier task groups of the Pacific Fleet during World War Two. After 1942, mounts like the Quad 40 were added in response to fierce Imperial Japanese air attacks and suicidal Kamikaze attacks in the Pacific campaign. Wisconsin had originally been designed for fewer than 1,550 crewmen, but the added antiaircraft emplacements required another 1,925 sailors to operate the guns, leaving more than 3,000 bluejackets crowded into every available space aboard ship during the war.
