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.

Background
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 Lord Nelson-class battleship 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.

Ammunition
The gun originally fired a 100 lb shell, which had been the standard shell weight for six-inch guns since 1880. From 1942 the gun fired the same 112 lb shell introduced for the later Mk XXIII gun. Figures in the table below are for the 100lb shell.

Weapons of comparable role, performance and era

 * 152 mm /53 Italian naval gun Models 1926 and 1929 approximate Italian equivalent deployed on light cruisers
 * 6"/53 caliber gun : roughly equivalent US gun deployed on light cruisers