The secondary armament was later upped to fourteen 6"/53 caliber guns in Mark 13 casemate mountings during one of the redesigns. Designed in 1920 and in service by 1923, these guns became the main armament on the light cruisers, , , and submarines, and they were intended as secondary armament on the South Dakota-class battleships.Morison and Polmar (2003), pp. 69–71Campbell (1985), pp. 132–33 They fired a shell at a muzzle velocity of 3,000 fps (914 mps) and a rate of six or seven rounds per minute to a range of at an elevation of 30 degrees.
