 Yorktown 's secondary battery consisted of two 6 @-@ pounder ( 57 mm ( 2 @.@ 24 in ) ) guns , two 3 @-@ pounder ( 47 mm ( 1 @.@ 85 in ) ) guns , and two 1 @-@ pounder ( 37 mm ( 1 @.@ 46 in ) ) guns . All were based on designs of the French arms company Hotchkiss . According to a 1902 Bureau of Ordnance publication , an armor @-@ piercing round fired from a 6 @-@ pounder gun could penetrate 2 inches ( 51 mm ) of armor at a distance of 1 @,@ 000 yards ( 910 m ) . 
