| Ordnance BL 6-inch gun Mk XXII | |
| Origin: | United Kingdom |
| Type: | Naval gun |
| Is Ranged: | yes |
| Is Artillery: | yes |
| Is Uk: | yes |
| Service: | 1927 – 1947 |
| Used By: | United Kingdom |
| Wars: | World War II |
| Design Date: | 1921 |
| Number: | 40 |
| Variants: | Mark XXII* |
| Weight: | 19,824 lbs. (8,992 kg) |
| Part Length: | 300inches bore (50 calibres) |
| Cartridge: | 1927 : 100lb 1942 : 112lb[1] |
| Caliber: | 6sigfig=4NaNsigfig=4 |
| Rate: | 5 rpm |
| Velocity: | 898m/s |
| Breech: | 364 lbs. (165.1 kg) Welin interrupted screw |
| Recoil: | 16.5 in (42 cm) |
| Elevation: | -5 / +60 degrees |
| Traverse: | +100 / -100 degrees |
The BL 6-inch Mk XXII gun[2] 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.[3] 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 100lb shell, which had been the standard shell weight for six-inch guns since 1880. From 1942 the gun fired the same 112lb shell introduced for the later Mk XXIII gun.[4] Figures in the table below are for the 100lb shell.
| Range | Elevation | Time of flight | Descent | Impact velocity | |
|---|---|---|---|---|---|
| 5000 yd (4.6 km) | 2° 5.2′ | 6.20 sec | 2° 48′ | 2029 ft/s (618 m/s) | |
| 10000 yd (9.1 km) | 5° 37.2′ | 15.22 sec | 9° 13′ | 1390 ft/s (424 m/s) | |
| 15000 yd (14 km) | 12° 5.4′ | 28.55 sec | 23° 2′ | 1094 ft/s (333 m/s) | |
| 20000 yd (18 km) | 22° 54′ | 46.14 sec | 39° 46′ | 1056 ft/s (322 m/s) | |
| 25000 yd (22.86 km) | 42° 37′ | 74.92 sec | 59° 0′ | 1148 ft/s (350 m/s) |