High Quality Content by WIKIPEDIA articles! The BL 6 inch guns Marks II, III, IV and VI were the second and subsequent generations of British 6-inch breechloading naval guns, designed by the Royal Gun Factory following the first 6-inch breechloader, the relatively unsuccessful BL 6 inch 80 pounder gun designed by Elswick Ordnance. They were originally designed to use the old gunpowder propellants. They were superseded on new warships by the QF 6 inch gun from 1891.