South Dakota was built as a fleet flagship, with an extra deck on her conning tower for extra command space, so her secondary battery had sixteen 5-in (127 mm)/38 caliber Mark 12 guns in eight Mark 28 Mod 0 twin DP mounts, four on either side of the superstructure.
This was two turrets fewer than her sister ships who had ten twin DP mounts of twenty guns, five on either side of the ship.
These turrets weighed 156,295 lb (70,894 kg) and could depress their guns to −15 degrees and elevate them to 85 degrees.
The guns fired a variety of different projectiles, including anti-aircraft (AA), illumination, and white phosphorus (WP) shells, at a rate of fire of 15 to 22 rounds per minute.
The AA shells were 20.75 in long (52.7 cm) and weighed between 54 and 55 lb (24–25 kg), depending on the variant.
The illumination and white phosphorus shells were slightly smaller, at 20 in (50.8 cm) long; the illumination rounds weighed 54.4 lb (24.7 kg) and the WP shells were 53 lb (24 kg).

The guns used three different charges, depending on the situation: a full charge, a full flashless charge, and a reduced charge.
The standard full charge weighed 15.2–15.5 lb (6.9–7.0 kg), the flashless charge was slightly heavier at 16 lb (7.3 kg), and the reduced charge was significantly smaller, at 3.6 lb (1.6 kg).
Both full charges provided a muzzle velocity of 2,600 ft/s (790 m/s) in new guns, but as continued fire wore down the barrels, muzzle velocity degraded slightly, to 2,500 ft/s (760 m/s).
The reduced charge's muzzle velocity was correspondingly lower, at 1,200 ft/s (370 m/s).
Each gun was supplied with 450 rounds, and was expected to fire 4,600 shells before it was worn enough to warrant replacement.
At the maximum effective elevation to engage surface targets, 45 degrees, the guns could hit targets up to 17,392 yards (15,903 m) away.
The maximum height at which aircraft could be engaged was 37,200 feet (11,900 m).
South Dakota was built as a fleet flagship, with an extra deck on her conning tower for extra command space, so her secondary battery had sixteen 5-in (127 mm)/38 caliber Mark 12 guns in eight Mark 28 Mod 0 twin DP mounts, four on either side of the superstructure. This was two turrets fewer than her sister ships who had ten twin DP mounts of twenty guns, five on either side of the ship. These turrets weighed 156,295 lb (70,894 kg) and could depress their guns to −15 degrees and elevate them to 85 degrees. The guns fired a variety of different projectiles, including anti-aircraft (AA), illumination, and white phosphorus (WP) shells, at a rate of fire of 15 to 22 rounds per minute. The AA shells were 20.75 in long (52.7 cm) and weighed between 54 and 55 lb (24–25 kg), depending on the variant. The illumination and white phosphorus shells were slightly smaller, at 20 in (50.8 cm) long; the illumination rounds weighed 54.4 lb (24.7 kg) and the WP shells were 53 lb (24 kg).
The guns used three different charges, depending on the situation: a full charge, a full flashless charge, and a reduced charge. The standard full charge weighed 15.2–15.5 lb (6.9–7.0 kg), the flashless charge was slightly heavier at 16 lb (7.3 kg), and the reduced charge was significantly smaller, at 3.6 lb (1.6 kg). Both full charges provided a muzzle velocity of 2,600 ft/s (790 m/s) in new guns, but as continued fire wore down the barrels, muzzle velocity degraded slightly, to 2,500 ft/s (760 m/s). The reduced charge's muzzle velocity was correspondingly lower, at 1,200 ft/s (370 m/s). Each gun was supplied with 450 rounds, and was expected to fire 4,600 shells before it was worn enough to warrant replacement. At the maximum effective elevation to engage surface targets, 45 degrees, the guns could hit targets up to 17,392 yards (15,903 m) away. The maximum height at which aircraft could be engaged was 37,200 feet (11,900 m).
South Dakota-class battleship (1939)