 These problems influenced the British to equip ships with muzzle @-@ loading weapons of increasing power until the 1880s . After a brief introduction of 100 @-@ pounder or 9 @.@ 5 @-@ inch ( 240 mm ) smoothbore Somerset Gun , which weighed 6 @.@ 5 tons ( 6 @.@ 6 t ) , the Admiralty introduced 7 @-@ inch ( 178 mm ) rifled guns , weighing 7 tons . These were followed by a series of increasingly <unk> weapons — guns weighing 12 , 25 , 25 , 38 and finally 81 tons , with calibre increasing from 8 @-@ inch ( 203 mm ) to 16 @-@ inch ( 406 mm ) . 
