The Mark 7 16-inch/50-caliber gun was the primary armament of the IOWA-class battleships. The IOWA class are the only battleships to mount this weapon which is a considerable improvement over the 16in/45cal guns mounted in the North Carolina and South Dakota classes. The Mark 7 gun fires two basic rounds, a 2,700 pound AP (Armor Piercing), which can penetrate up to 30 feet of concrete, and a 1,900 pound HC (High Capacity) shore bombardment projectile. The silk bags of propellant and the projectiles are elevatored to this room from the powder magazines and the shell decks below and then loaded into the gun in the gun room. To fire it, the gunner and his numerous mates complete a carefully choreographed sequence of events, first sliding the projectile into the breech, then gingerly placing the cylindrical silk bags of black powder, then ratcheting the breech shut. An ominous red stripe on the wall of the turret just inches from the railing marks the boundary of the gun's recoil.