Ordnance QF 20-pounder
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|Ordnance QF 20 pounder Mark I|
|Place of origin||United Kingdom|
|Used by||United Kingdom|
South African Border War
|Length||226.4 in (5.75 m), 66.7 calibres|
|Calibre||84 millimetres (3.31 in)|
|Elevation||+18 to −10 in Centurion Mk 5|
The Ordnance QF 20 pounder (known as 20 pounder, 20 pdr or simply 20-pr) was a British 84 mm (3.307 inch) tank gun.[i] It was introduced in 1948 and used in the Centurion main battle tank, Charioteer medium tank, and Caernarvon Mark II heavy tank. The 20 pounder was designed to replace the effective Ordnance QF 17 pounder, which had proven itself in World War II. However, once the gun was found to have inadequate performance against the Soviet T-54, the gun was mostly replaced in service by the larger calibre 105 mm L7 gun.
Design and development
The gun was developed by the Royal Ordnance Factories.
As fitted to the Charioteer, it ran through two models:
- Model A without a fume extractor.
- Model B with a fume extractor.
The gun was fitted predominantly to the Centurion tank, seeing action with British and Australian forces during the Korean and Vietnam War. When a Soviet T-54A main battle tank was driven to the British embassy in Budapest by Hungarian rebels during the Hungarian Revolution of 1956, analysis of its armour and 100 mm gun led British officials to determine that the 20 pounder was ineffective at defeating Soviet armour. This led to the development of the 105 mm L7 tank gun, which was designed to fit specifically into the turret mountings of the 20 pounder, facilitating for easily upgunning existing tanks equipped with the 20 pounder. 
The 20 pounder's APCBC projectile had an initial muzzle velocity of 1,020 metres per second and could penetrate 210 mm (8.3 in) of rolled homogeneous armour (RHA). However, these conventional rounds were rarely used.
- The gun is specified as 83.4 mm (3.283 in) here, while Ogorkiewiecz states the weapon was 83.8 mm. Norman gives it as "3.3 inch (84 mm)"
- The 20 pounder's APDS round had twice the penetration capability of an 8.8 cm AP round.
- Pugh (1962), p. 34.
- Ogorkiewicz (1991), p. 70.
- Zaloga, Steve, 1952- (2004). T-54 and T-55 main battle tanks 1944-2004. Johnson, Hugh, 1971-. Oxford: Osprey. ISBN 1841767921. OCLC 60834392.CS1 maint: Multiple names: authors list (link)
- Ford (1997), p. 121.
- "British Anti-Tank Gunnery Data". figuras.miniatures.de.[unreliable source?]
- Dunstan (2003), p. 10.
- Archive:Tank effectiveness: Conqueror, Conway and Charioteer & WO 291/1416 (1954), p. 9.
- Norman (1967), p. 12.
- Dunstan, Simon (2003). Centurion Universal Tank 1943-2003. Oxford, UK: Osprey Publishing. ISBN 1-84176-387-X..
- Ford, Roger (1997). The World's Great Tanks from 1916 to the present day. Brown Packaging Books Ltd. ISBN 1-897884-29-X.
- Norman, Michael (1967). Armour in Profile (Number 23), Centurion 5. Surrey: Profile Publications Ltd.
- Ogorkiewicz, Richard (1991). Technology of Tanks. London, UK: Jane's Information Group, Ltd. ISBN 0-7106-0595-1..
- Pugh, Stevenson (1962). Fighting Vehicles and Weapons of the Modern British Army. Macdonald & Co. OCLC 10010960.
- Pounds as a measure of cannon bore
- British standard ordnance weights and measurements
- Ordnance QF 32-pounder
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