BL 6-inch Mk XXII naval gun  The BL 6-inch Mk XXII gun was a British high-velocity 6-inch 50-calibre wire-wound naval guns deployed on the "Nelson"-class battleships from the 1920s to 1945. They were originally designed as secondary armament for the proposed G3 class battlecruisers. When the G3 class were cancelled after the Washington Naval Treaty the guns and mountings were later used as secondary armament on the two "Nelson"-class battleships, serving throughout World War II. The Nelsons were the first British battleships since the of 1904 to carry their secondary armament in turrets rather than in broadside casemates. The Mk VIII gun mountings could elevate from +60 degrees to -5 degrees, while the telescopic power rammers for the gun loaded at a +5-degree fixed angle. Although classified as a dual-purpose gun and capable of high-angle fire, their training and elevation speeds were too slow for the anti-aircraft role and their main use was against surface targets. The gun originally fired a shell, which had been the standard shell weight for six-inch guns since 1880. From 1942 the gun fired the same shell introduced for the later Mk XXIII gun. Figures in the table below are for the 100lb shell.