BL 8-inch Mk VIII naval gun explained

Ordnance BL 8 inch gun Mk VIII
Origin:	United Kingdom
Type:	Naval gun Coast defence gun
Is Ranged:	YES
Is Artillery:	YES
Is Uk:	YES
Service:	1927 – 1954^[1]
Used By:	Royal Navy Royal Australian Navy Spanish Navy
Wars:	Second World War Spanish Civil War
Number:	168^[2]
Weight:	17.5 tonnes
Part Length:	400 inches/10 meters(50 calibres)
Cartridge:	256lb
Caliber:	8adj=onNaNadj=on
Velocity:	2805 feet per second (855 m/s)
Max Range:	28km (17miles)

The BL 8 inch gun Mark VIII^[3] was the main battery gun used on the Royal Navy's cruisers,^[4] 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 8inch 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 cruisers.^[5] 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.^[6]

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 15abbr=onNaNabbr=on of cordite were used to fire a 116abbr=onNaNabbr=on 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 . 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.^[7]

• 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]

Shell trajectory

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

Range	Elevation	Time of flight	Descent	Impact velocity
5000abbr=onNaNabbr=on	2° 11	6 s	2° 31	2154 ft/s (657 m/s)
10000abbr=onNaNabbr=on	5° 14	14 s	7° 15	1683 ft/s (513 m/s)
15000abbr=onNaNabbr=on	9° 47	25 s	15° 49	1322 ft/s (403 m/s)
20000abbr=onNaNabbr=on	16° 34	38 s	28° 31	1169 ft/s (356 m/s)
25000abbr=onNaNabbr=on	26° 44	56 s	43° 7	1164 ft/s (355 m/s)
29000abbr=onNaNabbr=on	41° 28	79 s	56° 37	1240 ft/s (378 m/s)

See also

Weapons of comparable role, performance and era

• 203mm/50 Modèle 1924 gun French equivalent
• 20.3 cm SK C/34 Naval gun German equivalent
• 203 mm /53 Italian naval gun Italian equivalent
• 20 cm/50 3rd Year Type naval gun Japanese equivalent
• 8"/55 caliber gun US equivalent

Surviving examples

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

Bibliography

• Book: Naval Weapons of World War Two . Campbell, John . Naval Institute Press . 1985 . 0-87021-459-4.
• Book: British and Dominion Warships of World War Two . Lenton, H.T. . Colledge, J.J. . amp . Doubleday and Company . 1968.
• Book: Cruisers of World War Two . Whitley, M.J. . Brockhampton Press . 1995 . 1-86019-8740.

External links

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

Notes and References

1. Whitley 1995 pp.17,83&89
2. Campbell 1985 pp.31–33
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".
5. Campbell 1985 p.389
6. Whitley 1995 pp.96–127
7. Lenton & Colledge 1968 pp. 36–39