Like all modern battleships, USS Massachusetts was designed to engage and destroy enemy capital ships in decisive gun battles with her main battery: nine 16" guns mounted in three triple-turrets. However, such opportunities were few and far between, and battleships were assigned other important duties such as bolstering air defense for carriers and bombarding enemy shore fortifications in preparation for amphibious landings.

To fulfill these roles, BB59 employed the following weapons systems (c. 1946):

• nine 16" 45-caliber guns in triple mounts
• twenty 5" guns in dual mounts
• sixty 40MM guns in quadruple mounts
• twenty-two 20MM guns in single mounts
• eight 20MM guns in twin mounts

The #3 turret on USS Massachusetts.

FIGHTING WORDS: What is the difference between a "turret" and a "mount"? Consisting of several heavy guns (usually 6" or greater) in an armored housing, a turret is massive enough to require its inclusion in the shipbuilding process.

The 16/45 triple turrets were built into the USS North Carolina and Washington as well as the South Dakota-class battleships. With the exception of the 16/50 guns of the Iowa-class battleships, the contained the largest guns used in US Navy history. While the guns were the same in the North Carolina and South Dakota class battleships, the turret armor in the latter was thicker.

On BB59, three 16", 45 caliber guns are mounted in each turret. Each gun is mounted in a separate sleeve called a "slide." On firing, each gun recoiled four feet in its slide. Each slide has a pair of pivots called "trunnions," which allow each gun to elevate independent of the other two guns.