 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 Omaha @-@ class light cruisers , Narwhal , Nautilus , and Argonaut submarines , and they were intended as secondary armament on the South Dakota @-@ class battleships . They fired a 105 @-@ pound ( 48 kg ) 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 25 @,@ 300 yards ( 23 @,@ 100 m ) at an elevation of 30 degrees . 
