Ordnance QF 20 pounder

The Ordnance QF 20 pounder (simply known as 20 pounder or 20-pdr) was a British 84 mm (3.307 inch) tank gun introduced in 1948 and used in the Centurion tank and the Charioteer tank destroyer. It was the improved successor to the effective Ordnance QF 17 pounder and the predecessor of the 105 mm L7 gun.

Design and development
The 20 pounder's design followed that of the German 8.8 cm KwK 43, a cannon used in the Second World War Tiger series tanks. Like the KwK 43, the 20 pounder had a length of 66.7 calibres and could fire both APCBC and sub-calibre rounds. The 20 pounder's APCBC projectile had a muzzle velocity of 1,020 meters per second and could penetrate 21 cm of rolled homogeneous armour (RHA) while the APDS projectile had a muzzle velocity of 1,465 m/s and could penetrate 30 cm of RHA. The 20-pounder could also fire high-explosive and canister shot.

The L7 105 mm tank gun was developed in 1954 from the 20 pounder by re-boring the tube.

The gun was fitted to the Swiss pre-production Panzer 58.