The Mark 8 was a 2,700-pound armor-piercing projectile fired from one of the nine 16-inch, 45-caliber Mark 45 "Big Guns" aboard the battleship USS Alabama (BB 60). It traveled at 2,300 feet per second, or 1,568 miles per hour, more than twice the speed of sound, and the guns were accurate at ranges up to 20.97 miles from the battleship.