Ordnance QF 20-pounder
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The Ordnance QF 20 pounder was a British 84 mm tank gun. It was introduced in 1948 and used in the Centurion main battle tank, Charioteer medium tank, and Caernarvon Mark II heavy tank. Wikipedia
Barrel length: 226.4 in (5.75 m), 66.7 calibres
Calibre: 84 millimetres (3.31 in)
Shell: 84×618mm R
Used by: United Kingdom; Australia; Austria; Canada; Finland; Israel; Jordan; Lebanon; South Africa