BL 8-inch Mk VIII naval gun

Ordnance BL 8 inch gun Mk VIII
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
Used by	Royal Navy ; Royal Australian Navy ; Spanish Navy
Wars	Second World War ; Spanish Civil War
Production history
No. built	168
Specifications
Mass	17.5 tonnes
Barrel length	400 inches/10 meters(50 calibres)
Shell	256 pounds (116 kg)
Calibre	8-inch (203 mm)
Muzzle velocity	2805 feet per second (855 m/s)
Maximum firing range	28 kilometres (17 mi)

The BL 8 inch gun Mark VIII^{[note 1]} was the main battery gun used on the Royal Navy's County-class 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 (203 mm) 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 guns, 50 calibres long, were built-up guns which 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 lb) of cordite were used to fire a 116 kg (256 lb) 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 version of the Mark II turrets with a maximum elevation of 50 degrees were installed in 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 : 13 ships
- Canarias-class heavy cruisers : 2 ships
York-class heavy cruisers : 2 ships

Coast defence guns

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 with 256 lbs. (116.1) SAPC with MV = 2,725 fps (831 mps)

Range^[2]	Elevation	Time of flight	Descent	Impact velocity
5,000 yd (4,570 m)	2° 11′	6 s	2° 31′	2154 ft/s (657 m/s)
10,000 yd (9,140 m)	5° 14′	14 s	7° 15′	1683 ft/s (513 m/s)
15,000 yd (13,720 m)	9° 47′	25 s	15° 49′	1322 ft/s (403 m/s)
20,000 yd (18,290 m)	16° 34′	38 s	28° 31′	1169 ft/s (356 m/s)
25,000 yd (22,860 m)	26° 44′	56 s	43° 7′	1164 ft/s (355 m/s)
29,000 yd (26,520 m)	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
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j 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

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

[3] 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.

[4] 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".

[Whitley-1] Whitley 1995 pp.17,83&89

[Campbell-2] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Campbell 1985 pp.31–33

[Campbell389-5] Campbell 1985 p.389

[Whitley1-6] Whitley 1995 pp.96–127

[L&C-7] Lenton & Colledge 1968 pp. 36–39

[1]

[2]

[note 1]

[note 2]

[3]

[4]

[5]

v t e 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 5.5-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)

v t e 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