The primary armament of an Iowa-class battleship is nine 16 inch (406 mm) / 50-caliber Mark 7 naval guns, which are housed in three 3-gun turrets: two forward and one aft in a configuration known as "2-A-1". The guns are 66 feet (20 m) long (50 times their 16 inch bore, or 50 calibers, from breechface to muzzle). About 43 feet (13 m) protrudes from the gun house. Each gun weighs about 239,000 pounds (108 000 kg) without the breech, or 267,900 pounds with the breech.[28][29] They fire projectiles weighing from 1,900 to 2,700 pounds (850 to 1,200 kg) at a maximum speed of 2,690 ft/s (820 m/s) up to 24 nautical miles (39 km). At maximum range the projectile spends almost 1½ minutes in flight.

Each gun rests within an armored turret, but only the top of the turret protrudes above the main deck. The turret extends either four decks (Turrets 1 and 3) or five decks (Turret 2) down. The lower spaces contain rooms for handling the projectiles and storing the powder bags used to fire them. Each turret required a crew of 94 men to operate.[28] The turrets are not actually attached to the ship, but sit on rollers, which means that if the ship were to capsize the turrets would fall out.[30] Each turret costs US $1.4 million, but this number does not take into account the cost of the guns themselves[28]

The turrets are "three-gun", not "triple", because each barrel can be elevated independently; they can also be fired independently. The ship could fire any combination of its guns, including a broadside of all nine. Contrary to myth, the ships do not move noticeably sideways when a broadside is fired.[31]

The guns can be elevated from −5° to +45°, moving at up to 12° per second. The turrets can be rotated about 300° at about four degrees per second and can even be fired back beyond the beam, which is sometimes called "over the shoulder." The guns are never fired directly forward (in the 1980s refit, a satellite up-link antenna was mounted at the bow).