BL 6 inch Mk XXII naval gun

Ordnance QF 6 inch gun Mk XXII
Gun turrets on HMS Rodney, 1940
Type	Naval gun
Service history
In service	1927 - 1947
Used by	United Kingdom
Wars	World War II
Production history
Designed	1921
No. built	40
Variants	Mark XXII*
Specifications
Weight	19,824 lbs. (8,992 kg)
Barrel length	300 inches (7.620 m) bore (50 calibres)
Shell	1927 : 100 pounds (45 kg) 1942 : 112 pounds (51 kg)
Calibre	6-inch (152.4 mm)
Breech	364 lbs. (165.1 kg) Welin interrupted screw
Recoil	16.5 in (42 cm)
Elevation	-5 / +60 degrees
Traverse	+100 / -100 degrees
Rate of fire	5 rpm
Muzzle velocity	898 metres per second (2,950 ft/s)

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 Lord Nelson class 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 100-pound (45 kg) shell, which had been the standard shell weight for six-inch guns since 1880. From 1942 the gun fired the same 112-pound (51 kg) shell introduced for the later Mk XXIII gun. Figures in the table below are for the 100lb shell.