BL 8 inch Mk VIII naval gun

Ordnance BL 8 inch gun Mk VIII
Forward 8-inch turrets aboard HMAS Canberra
Type	Naval gun Coast defence gun
Place of origin	United Kingdom
Service history
In service	1927 - 1954^[1]
Used by	Royal Navy Royal Australian Navy
Wars	Second World War
Production history
Number built	168^[2]
Specifications
Weight	17.5 tonnes^[2]
Barrel length	400 inches/10 meters(50 calibres)^[2]

Shell	256 pounds (116 kg)
Calibre	8-inch (203 mm)^[2]
Muzzle velocity	2805 feet per second (855 m/s)^[2]
Maximum firing range	28 kilometres (17 mi)^[2]

The 50 calibre BL 8 inch gun Mark VIII^{[note 1]} was the main battery gun used on the Royal Navy's County-class heavy cruisers,^{[note 2]} in compliance with the Washington Naval Treaty of 1922. This treaty allowed ships of not more than 10,000 tons standard displacement and with guns no larger than 8 inches to be excluded from total tonnage limitations on a nation's capital ships. The 10,000 ton limit was a major factor in design decisions such as turrets and gun mountings. A similar gun formed the main battery of Spanish Canarias-class cruisers.^[3] In 1930, the Royal Navy adopted the BL 6 inch Mk XXIII naval gun as the standard cruiser main battery in preference to this 8-inch gun.^[4]

Description

These built-up guns consisted of a wire-wound tube encased within a second tube and jacket with a Welin breech block and hydraulic or hand-operated Asbury mechanism. Two cloth bags each containing 15 kg (33 pounds) of cordite were used to fire a 116-kg (256-pound) projectile. Mark I turrets allowed gun elevation to 70 degrees to fire high-explosive shells against aircraft. Hydraulic pumps proved incapable of providing sufficient train and elevation speed to follow contemporary aircraft; so simplified Mark II turrets with a maximum elevation of 50 degrees were installed in the Norfolk subgroup ships Dorsetshire and Norfolk and the York-class cruisers York and Exeter. Each gun could fire approximately five rounds per minute. Useful life expectancy was 550 effective full charges (EFC) per barrel.^[2]

Naval service

The following ships mounted Mk VIII guns in 188-tonne twin turrets.^[2] The standard main battery was four turrets, but Exeter and York carried only three to reduce weight and formed the separate York class.^[5]

County-class heavy cruisers : 14 ships
York-class heavy cruisers : 2 ships

Coast defence guns

Gun of 428 Battery Coast Defence Artillery firing at dusk during World War II

Six single guns capable of elevating to 70 degrees were installed as coastal artillery in the Folkestone-Dover area during the Second World War.^[2]

Ammunition

World War II semi-armour-piercing shell with marker dye to identify ship that fired it for range corrections
1930s high-explosive shell
Coast-defence gun shells, World War II

Shell trajectory

Range^[2]	Elevation	Time of flight	Descent	Impact velocity
5000 yd (4.6 km)	2° 11′	6 s	2° 31′	2154 ft/s (657 m/s)
10000 yd (9.1 km)	5° 14′	14 s	7° 15′	1683 ft/s (513 m/s)
15000 yd (14 km)	9° 47′	25 s	15° 49′	1322 ft/s (403 m/s)
20000 yd (18 km)	16° 34′	38 s	28° 31′	1169 ft/s (356 m/s)
25000 yd (23 km)	26° 44′	56 s	43° 7′	1164 ft/s (355 m/s)
29000 yd (27 km)	41° 28′	79 s	56° 37′	1240 ft/s (378 m/s)

Surviving examples

A gun from HMAS Australia outside the Australian War Memorial, Canberra

Notes

↑ Mark VIII = Mark 8. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence this was the eighth model of BL 8-inch naval gun.
↑ A more accurate term is "Treaty Cruiser", as the term heavy cruiser was only formally defined at the time of the London Naval Treaty of 1930. However, all the 8-inch gun cruisers introduced as a result of the 1922 Washington Treaty were what became known as "heavy cruisers".

References

↑ Whitley 1995 pp.17,83&89
1 2 3 4 5 6 7 8 9 10 Campbell 1985 pp.31-33
↑ Campbell 1985 p.389
↑ Whitley 1995 pp.96-127
↑ Lenton & Colledge 1968 pp.36-39

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.
Whitley, M.J. (1995). Cruisers of World War Two. Brockhampton Press. ISBN 1-86019-8740.

External links

Wikimedia Commons has media related to BL 8 inch Mk VIII naval gun.

Tony DiGiulian, Britain 8"/50 (20.3 cm) Mark VIII
Terry Gander, Twentieth century British coast defence guns

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 pdr 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 pdr 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 2inch 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 18 inch railway howitzer

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