 The ship 's main armament consisted of four smoothbore , muzzle @-@ loading 11 @-@ inch Dahlgren guns mounted in two twin @-@ gun turrets . Her forward turret was designed by James Eads and her rear turret by John Ericsson . Each gun weighed approximately 16 @,@ 000 pounds ( 7 @,@ 300 kg ) and could fire a 136 @-@ pound ( 61 @.@ 7 kg ) shell up to a range of 3 @,@ 650 yards ( 3 @,@ 340 m ) at an elevation of + 15 ° . 
