BL 7.5-inch Mk VI naval gun

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Ordnance BL 7.5-inch gun Mk VI
The Royal Navy during the Second World War A24095.jpg
Gun on HMS Frobisher off the south coast of England, 5 June 1944, 12 hours before D-Day
Type Naval gun
Coast defence gun
Place of originUnited Kingdom
Service history
In service1919–1945 [1]
Used by Royal Navy
Wars World War II
Production history
No. built44 [2]
Specifications
Mass14 tonnes (14,000 kg) [2]
Barrel  length337.5 inches (8.6 m); (45 calibres) [2]

Shell 200 pounds (91 kg) [2]
Calibre 7.5-inch (190 mm) [2]
Muzzle velocity 2,770 feet per second (844 m/s) [2]
Maximum firing range12 miles (19 km) [2]

The BL 7.5-inch gun Mark VI [3] was the 45 calibre naval gun forming the main battery of Royal Navy Hawkins-class cruisers. These ships with seven single gun mounts were significant to the cruiser limitations defined by the Washington Naval Treaty. [4]

Contents

Description

These were built-up guns with two tubes, full-length wire winding, a jacket, and Welin breech block with hand-operated Asbury mechanism. The mounting was a CP Mk V a hand-operated central pivot mount with additional power training and elevation provided by a 10HP electric motor and hydraulic pump. Elevation was +30 degrees to -5 degrees and loading was possible up to +10 degrees. The total weight of the mount including its 1in open-backed shield was 45.975 tons. They used two cloth bags each containing 14 kg (31 pounds) of cordite to fire a 200-pound (91-kg) projectile up to 19 kilometres at their maximum elevation of 30 degrees. Useful life expectancy was 650 effective full charges (EFC) per barrel. [2]

Coast defence guns

Seven guns were installed as coastal artillery in the Netherlands Antilles, five in Mozambique, three in Canada, and three in a battery at South Shields during the Second World War. [2]

Shell trajectory

Range [2] ElevationTime of flightDescentImpact velocity
5000 yd (4.6 km) 30′7 sec 19′1799 ft/s (548 m/s)
10000 yd (9.1 km) 3′17 sec12° 32′1218 ft/s (371 m/s)
15000 yd (14 km)15° 21′32 sec27° 33′1038 ft/s (316 m/s)
20000 yd (18 km)27° 59′51 sec44° 35′1071 ft/s (326 m/s)

See also

Notes and references

  1. Whitley 1995 pp.77–80
  2. 1 2 3 4 5 6 7 8 9 10 Campbell 1985 p.33
  3. Mark VI = Mark 6. Britain used Roman numerals to denote Mark (models) of ordnance until after World War II. This was the 6th model of BL 7.5-inch naval gun.
  4. Preston 1980 pp.69–70

Bibliography

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