BL 7.5-inch Mk VI naval gun

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
Type	Naval gun Coast defence gun
Place of origin	United Kingdom
Service history
In service	1919–1945[1]
Used by	Royal Navy
Wars	World War II
Production history
No. built	44[2]
Specifications
Mass	14 tonnes (14,000 kg)[2]
Barrel length	337.5 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 range	12 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]

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]	Elevation	Time of flight	Descent	Impact velocity
5000 yd (4.6 km)	2° 30′	7 sec	3° 19′	1799 ft/s (548 m/s)
10000 yd (9.1 km)	7° 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

• List of naval guns
• BL 7.5-inch Mk II – V naval gun (earlier Royal Navy guns of the same calibre)
• BL 8-inch Mk VIII naval gun (used on subsequent Royal Navy heavy cruisers)

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

Bibliography

• 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, Antony (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.

External links

• Tony DiGiulain, Britain 7.5"/45 (19 cm) Mark VI