|Ordnance BL 8 inch gun Mk VIII|
Mk VIII guns in X and Y Mk I turrets aboard HMS Kent
Coast defence gun
|Place of origin||United Kingdom|
|In service||1927 - 1954|
|Used by|| Royal Navy|
Royal Australian Navy
|Wars||Second World War|
|Barrel length||400 inches (10 meters)|
|Shell||256 pounds (116 kg)|
|Calibre||8-inch (203 mm)|
|Muzzle velocity||2805 feet per second (855 m/s)|
|Maximum range||28 kilometres (17 mi)|
The 50 calibre BL 8 inch gun Mark VIII was the main battery gun used on the Royal Navy's County-class heavy cruisers, 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. 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.
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.
The following ships mounted Mk VIII guns in 188-tonne twin turrets. The standard main battery was four turrets, but Exeter and York carried only three to reduce weight and formed the separate York class.
Coast defence guns
|Range||Elevation||Time of flight||Descent||Impact velocity|
|5000 yd (4.6 km)||2° 11′||6 sec||2° 31′||2154 ft/s (657 m/s)|
|10000 yd (9.1 km)||5° 14′||14 sec||7° 15′||1683 ft/s (513 m/s)|
|15000 yd (14 km)||9° 47′||25 sec||15° 49′||1322 ft/s (403 m/s)|
|20000 yd (18 km)||16° 34′||38 sec||28° 31′||1169 ft/s (356 m/s)|
|25000 yd (23 km)||26° 44′||56 sec||43° 7′||1164 ft/s (355 m/s)|
|29000 yd (27 km)||41° 28′||79 sec||56° 37′||1240 ft/s (378 m/s)|
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
- Whitley 1995 pp.17,83&89
- Campbell 1985 pp.31-33
- 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".
- Campbell 1985 p.389
- Whitley 1995 pp.96-127
- Lenton & Colledge 1968 pp.36-39
- 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.
|Wikimedia Commons has media related to BL 8 inch Mk VIII naval gun.|
- Tony DiGiulian, Britain 8"/50 (20.3 cm) Mark VIII
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