BL 7.5-inch Mk VI naval gun

Ordnance BL 7.5-inch gun Mk VI
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)

Notes and references

Whitley 1995 pp.77–80
Campbell 1985 p.33
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.
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, 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.

External links

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

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[Whitley-1] Whitley 1995 pp.77–80

[Campbell-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.

[Preston-4] Preston 1980 pp.69–70

British Commonwealth naval weapons of the Second World War
Monitor guns	BL 15-inch
Capital ship main armament	BL 14-inch BL 15-inch BL 16-inch
Heavy cruiser main armament	BL 7.5-inch Mk VI BL 8-inch Mk VIII
Secondary armament and light cruiser main armament	QF 4-inch Mk V QF 4.5-inch QF 5.25-inch BL 6-inch Mk XII BL 6-inch Mk XXII BL 6-inch Mk XXIII
Minesweeper, Sloop, Corvette, Frigate and Destroyer armament	QF 6-pounder 10 cwt QF 12-pounder 12 cwt Mk V QF 4-inch Mk IV BL 4-inch Mk IX QF 4-inch Mk XVI QF 4-inch Mk XIX QF 4.5-inch BL 4.7-inch Mk II QF 4.7-inch Mk IX & XII QF 4.7-inch Mk XI
Submarine guns	QF 12-pounder 12 cwt Mk V QF 3-inch 20 cwt QF 4-inch Mk XII & XXII
Anti-aircraft weapons	Unrotated projectile Holman Projector 20 mm Oerlikon QF 2-pounder "pom-pom" Mk VIII 40 mm Bofors QF 3-inch 20 cwt QF 4-inch Mk V QF 4-inch Mk XVI QF 4.5-inch QF 4.7-inch Mk VIII
Light weapons	.303 Lewis machine gun .50 Vickers Mk III machine gun QF 3-pounder Vickers
Torpedoes	21-inch Mk VII 21-inch Mk VIII 21-inch Mk X 21-inch Mk XI 24.5-inch Mk I
Anti-submarine weapons	Thornycroft depth charge thrower Hedgehog Squid
Small craft armament	Molins 6-pounder Vickers K machine gun 18-inch torpedo
Foreign-sourced weapons	20 mm Oerlikon 40 mm Bofors 3-inch 23 caliber gun (US) 3-inch 50 caliber gun (US) 4-inch 50 caliber Mark 9 gun (US) 5-inch 51 caliber Mark 8 gun (US) Y-gun depth charge projector (US) Mark 8 torpedo (US)

British Commonwealth artillery of World War II
Tank guns	QF 2-pounder QF 3-pounder QF 6-pounder QF 75 mm QF 3-inch howitzer QF 17-pounder 77 mm HV QF 95 mm howitzer
Anti-tank guns	QF 2-pounder QF 6-pounder QF 17-pounder
Field guns and howitzers	75 mm Gun M1917 QF 18-pounder 25-pounder Gun-Howitzer 25-pounder Short QF 4.5-inch howitzer
Medium and heavy guns and howitzers	BL 4.5-inch Medium Field Gun BL 60-pounder gun BL 5.5-inch Medium Gun BL 6-inch howitzer BL 6-inch gun Mk XIX 155 mm Long Tom BL 7.2-inch howitzer BL 8-inch howitzer BL 9.2-inch howitzer 240 mm howitzer M1
Mountain guns	75mm Pack howitzer M1 3.7-inch mountain howitzer
Mortars	SBML 2-inch mortar ML 3-inch mortar ML 4.2-inch mortar
Anti-aircraft weapons	Z Battery 20 mm Oerlikon 20 mm Polsten QF 1½-pounder Mk III QF 2-pounder naval gun Bofors 40 mm QF 3-inch QF 3.7-inch QF 4.5-inch Mk II QF 5.25-inch Mk II
Coast defence	QF 6-pounder 10 cwt QF 12-pounder QF 4.7-inch Mk I–IV BL 6-inch Mk VII & Mk XXIV BL 7.5-inch Mk VI BL 8-inch Mk VIII BL 9.2-inch Mk X BL 14-inch Mk VII BL 15-inch Mk I
Railway artillery	BL 9.2-inch Mk XIII railway gun BL 12-inch Mk V railway howitzer BL 13.5-inch Mk V railway gun BL 18-inch railway howitzer