Ordnance QF 20 pounder

Ordnance QF 20 pounder Mark I
Charioteer tank equipped with the 20 pounder. This gun is a later model which is fitted with a bore evacuator
Type	tank gun
Place of origin	United Kingdom
Service history
In service	1948-1970s
Used by	United Kingdom  Australia  Austria  Canada  Finland  Israel  Jordan  Lebanon  South Africa
Wars	Korean War Vietnam War Six Day War South African Border War
Specifications
Length	226.4 in (5.75 m)
Shell	20 pounds (9.07 kg)
Calibre	84 millimetres (3.31 in)
Elevation	+18 to -10 in Centurion Mk 5

The Ordnance QF 20 pounder (simply known as 20 pounder or 20-pdr) was a British 84 mm (3.307 inch)^[1] tank gun introduced in 1948 and used in the Centurion main battle tank, Charioteer cruiser tank, and Caernarvon Mark II heavy tank. British engineers, after examining the German 8.8 cm Pak 43 anti-tank gun, decided to produce a new cannon for British tanks that would be an improvement over the 17 pounder, whose penetration was similar to that of the Panther tank's 7.5 cm KwK 42 gun,^[2] and the predecessor of the 105mm L7 gun.

Design and development

The 20 pounder's APCBC projectile had an initial muzzle velocity of 1,020 metres per second and could penetrate 210mm of rolled homogeneous armour (RHA). However, these conventional rounds were rarely used. The armour-piercing discarding sabot projectile had a muzzle velocity of 1,465 m/s (4,810 ft/s) and could penetrate 30 cm (12 in) of RHA.^[3][4] The 20-pounder could also fire high-explosive and canister shot shells.

The L7 105 mm tank gun was developed from the 20 pounder. In 1954, the original version of the 105 mm was made by re-boring the tube of a 20 pounder barrel.^[5]

One gun was fitted to a Swiss pre-production Panzer 58.^[6]

Ammunition

20 pdr HE round

Round	Muzzle velocity[7]
APDS	4,700 ft/s
HE	1,975 ft/s
Canister	3,000 ft/s
Smoke	825 ft/s

Notes

1. Pugh, p.34; 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)"
2. "WWII Ballistics: Armor and Gunnery". Scribd. Retrieved 2016-05-01.
3. British Anti-Tank Gunnery Data at www.figuras.miniatures.de
4. Dunstan, p. 10, notes the 20 pounder's APDS round had twice the penetration capability of an 8.8 cm AP round.
5. Ogorkiewicz, p. 70.
6. • Ford, Roger (1997). The World's Great Tanks from 1916 to the present day. Brown Packaging Books Ltd. p. 121. ISBN 1-897884-29-X.
7. Norman p12

References

• Dunstan, Simon. Centurion Universal Tank 1943-2003, Oxford: Osprey Publishing, 2003. ISBN 1-84176-387-X.
• Ogorkiewicz, Richard. Technology of Tanks, London: Jane's Information Group, Ltd., 1991. ISBN 0-7106-0595-1.
• Pugh, Stevenson (1962). Fighting Vehicles and Weapons of the Modern British Army. Macdonald & Co. OCLC 10010960.
• Norman, Michael. Armour in Profile No. 23 Centurion 5. Surrey: Profile Publications.

See also

• Pounds as a measure of cannon bore
• British standard ordnance weights and measurements
• Ordnance QF 32-pounder

External links