BL 7.5-inch Mk VI naval gun

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]

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

Shell200 pounds (91 kg)[2]
Calibre7.5-inch (190 mm)[2]
Muzzle velocity2,770 feet per second (844 m/s)[2]
Maximum firing range12 miles (19 km)[2]


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] Elevation Time of flight Descent Impact velocity
5000 yd (4.6 km)  30′ 7 sec  19′ 1799 ft/s (548 m/s)
10000 yd (9.1 km)  3′ 17 sec 12° 32′ 1218 ft/s (371 m/s)
15000 yd (14 km) 15° 21′ 32 sec 27° 33′ 1038 ft/s (316 m/s)
20000 yd (18 km) 27° 59′ 51 sec 44° 35′ 1071 ft/s (326 m/s)

See also

Notes and references

  1. Whitley 1995 pp.77–80
  2. 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


  • Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.
  • Lenton, H.T. & Colledge, J.J (1968). British and Dominion Warships of World War Two. Doubleday and Company.
  • Preston, Anthony (1980). Cruisers. Prentice-Hall. ISBN 0-13-194902-0.
  • Whitley, M.J. (1995). Cruisers of World War Two. Brockhampton Press. ISBN 1-86019-874-0.
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