The "South Dakota"-class battleships carried a main battery of nine 16-in (406 mm)/45 caliber Mark 6 guns in three three-gun turrets, identical to the "North Carolina"-class. Two of these turrets were placed in a superfiring pair forward; the third turret was mounted aft of the main superstructure. These guns fired a Mark 8 armor-piercing (AP) shell at a rate of two per minute per gun. The guns could either use a full propellant charge of , a reduced charge of , or a reduced flashless charge of . This provided a muzzle velocity of 2,300 feet per second (700 meters per second) for the AP shell with the full propellant charge, while the reduced version provided a correspondingly lower muzzle velocity of 1,800 ft/s (549 m/s). 130 shells were stowed for each gun, which came to a total of 1,170. The guns in all three turrets could elevate to 45 degrees, but only I and III turrets could depress to −2 degrees; the superfiring II turret was not able to depress. This enabled a maximum range of 36,900 yards or with the Mark 8 projectile. The turrets were able to 150 degrees in both directions from the centerline, which enabled a wide arc of fire. The guns could be elevated or depressed at a rate of 12 degrees per second, and the turrets could train at 4 degrees per second.