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 [1]
Used by	Royal Navy ; Royal Australian Navy
Wars	Second World War
Production history
No. 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]

Last updated March 12, 2019

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 (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]

The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by the English kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years War against the Kingdom of France. The modern Royal Navy traces its origins to the early 16th century; the oldest of the UK's armed services, it is known as the Senior Service.

The County class was a class of heavy cruisers built for the Royal Navy in the years between the First and Second World Wars. They were the first post-war cruiser construction for the Royal Navy and were designed within the limits of the Washington Naval Treaty of 1922. Such ships, with a limit of 10,000 tons, standard displacement and 8-inch calibre main guns may be referred to as "treaty cruisers".

The heavy cruiser was a type of cruiser, a naval warship designed for long range and high speed, armed generally with naval guns of roughly 203 mm (8 inches) in caliber, whose design parameters were dictated by the Washington Naval Treaty of 1922 and the London Naval Treaty of 1930. The heavy cruiser is part of a lineage of ship design from 1915 through the early 1950s, although the term "heavy cruiser" only came into formal use in 1930. The heavy cruiser's immediate precursors were the light cruiser designs of the 1900s and 1910s, rather than the armoured cruisers of before 1905. When the armoured cruiser was supplanted by the battlecruiser, an intermediate ship type between this and the light cruiser was found to be needed—one larger and more powerful than the light cruisers of a potential enemy but not as large and expensive as the battlecruiser so as to be built in sufficient numbers to protect merchant ships and serve in a number of combat theaters.

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 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 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]

A built-up gun is artillery with a specially reinforced barrel. An inner tube of metal stretches within its elastic limit under the pressure of confined powder gases to transmit stress to outer cylinders that are under tension. Concentric metal cylinders or wire windings are assembled to minimize the weight required to resist the pressure of powder gases pushing a projectile out of the barrel. Built-up construction was the norm for guns mounted aboard 20th century Dreadnoughts and contemporary railway guns, coastal artillery, and siege guns through World War II.

The Welin breech block was a revolutionary stepped, interrupted thread design for locking artillery breeches, invented by Axel Welin in 1889 or 1890. Shortly after, Vickers acquired the British patents. Welin breech blocks provide obturation for artillery pieces which use separate loading bagged charges and projectiles. In this system the projectile is loaded first and then followed by cloth bags of propellant.

An Asbury Mechanism opens and closes the breech of heavy artillery for reloading with a projectile and bags of propellant. It was widely used for naval artillery of the world wars and similar coastal artillery and railway guns. The device was invented at the Washington Navy Yard in 1916 by draftsman Dorsey Frost Asbury. It is sometimes called a Smith-Asbury mechanism by the United States Navy in recognition of Asbury's supervisor, Lieutenant Commander George Leonard Smith, USN.

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

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]

Coastal artillery is the branch of the armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications.

Folkestone town in the Shepway District of Kent, England

Folkestone is a port town on the English Channel, in Kent, south-east England. The town lies on the southern edge of the North Downs at a valley between two cliffs. It was an important harbour and shipping port for most of the 19th and 20th centuries.

Dover is a major ferry port in Kent, South East England. It faces France across the Strait of Dover, the narrowest part of the English Channel, and lies south-east of Canterbury and east of Maidstone. The town is the administrative centre of the Dover District and home of the Dover Calais ferry through the Port of Dover. The surrounding chalk cliffs are known as the White Cliffs of Dover.

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".

Related Research Articles

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The Town class was a 10-ship class of light cruisers of the Royal Navy. The Towns were designed to the constraints imposed by the London Naval Treaty of 1930. The ships were built in three distinct sub-classes, the Southampton, Gloucester and Edinburgh classes respectively, each sub-class adding on further weaponry.

The York class was the second and final class of 8-inch (203 mm)–gunned heavy cruisers built for the Royal Navy under the terms of the 1922 Washington Naval Treaty. They were essentially a reduced version of the preceding County class, scaled down to enable more cruisers to be built from the limited defence budgets of the late 1920s.

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The Hawkins class was a class of five heavy cruisers of the Royal Navy designed in 1915 and constructed throughout the First World War. All ships were named after Elizabethan sea captains. The three ships remaining as cruisers in 1939 served in the Second World War, with Effingham being an early war loss through wreck; Raleigh had been lost in a similar shipwreck on uncharted rocks in 1922. Vindictive, though no longer a cruiser, also served throughout the War. This class formed the basis for the definition of the maximum cruiser type under the Washington Naval Treaty of 1922.

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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

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

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[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] 1 2 3 4 5 6 7 8 9 10 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

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 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)

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 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 13.5 inch Mk V railway gun BL 18 inch railway howitzer