−5° to +45°, moving at up to 12° per second. The turrets would have rotated about 300° at about 4° per second and could even be fired back beyond the beam, which is sometimes called "over the shoulder". Within each turret, a red stripe on the wall of the turret, just inches from the railing, would have marked the boundary of the gun's recoil, providing the crew of each gun turret with a visual reference for the minimum safe distance range. Like most US battleships in World War II, the Montana class would have been equipped with a fire control computer—in this case, the Ford Instrument Company Mk 1A Ballistic Computer, a rangekeeper designed to direct gunfire on land, sea, and in the air. This analog computer would have been used to direct the fire from the battleship's main guns, taking into account several factors, such as the speed of the targeted ship, the time it takes for a projectile to travel, and air resistance to the shells fired at a target. At the time the Montana class was set to begin construction, the rangekeepers had gained the ability to use radar data to help target enemy ships and land-based targets. The results of this advance were telling: the rangekeeper was able to track and fire at targets at a greater range and with increased accuracy, as was demonstrated in November 1942 when the battleship engaged the Imperial Japanese Navy battleship at a range of at night; Washington scored at least nine heavy caliber hits that critically damaged the Kirishima and led to her loss. This gave the US Navy a major advantage in World War II, as the Japanese did not develop radar or automated fire control to the level of the US Navy. The large caliber guns were designed to fire two different 16-inch shells: an armor-piercing round for anti-ship and anti-structure work, and a high-explosive round designed for use against unarmored targets and shore bombardment. The Mk. 8 APC (Armor-Piercing, Capped) shell weighed in at and was designed to penetrate the hardened steel armor carried by foreign battleships. At , the Mk. 8 could penetrate of vertical steel armor plate. For unarmored targets and shore bombardment, the Mk. 13 HC (High-Capacity —referring to the large bursting charge) shell was available. The Mk. 13 shell could create a crater wide and deep upon impact and detonation and could