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)[1] 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.

Contents

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 King Tiger tank.[2] 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 (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.

The L7 105 mm tank gun was developed in 1954 from the 20 pounder by re-boring the tube.[2]

The gun was fitted to the Swiss pre-production Panzer 58[5].

Performance

Performance of 20-Pounder and comparable weapons against rolled homogeneous armor
Weapon Muzzle Velocity
metres/second		 Penetration
mm
20-Pounder (firing M3 APDS) 1,465 287 (at 90°, range 1,000 metres)[6]
85 mm D-48 (firing BR-372) 1,040 185 (at 90°, range 1,000 metres)
8.8 cm PaK 43 (firing PzGr 40/43) 1,130 193 (at 60°, range 1,000 metres)
90 mm M3 (firing M304) 1,021 195 (at 60°, range 914 metres)
These data are not directly comparable as various measurement methods are used.
They are, however, illustrative of the relative performance of the weapons.

Notes

  1. ^ Pugh, p.34; the gun is specified as 83.4 mm (3.283") here, while Ogorkiewiecz states the weapon was 83.8 mm.
  2. ^ a b Ogorkiewicz, p. 70.
  3. ^ British Anti-Tank Gunnery Data at www.figuras.miniatures.de
  4. ^ Dunstan, p. 10, also notes the 20 pounder's APDS round had twice the penetration capability of an 8.8 cm AP round. If one assumes Dunstan is referring to the 8.8 cm KwK 36 on the Tiger I, then 305 mm at 0° is in fact about twice the performance of the Tiger's AP round. The quoted figures refer to a range under 100 meters with the projectile striking the armor plate at an angle of 90 degrees.
  5. ^ *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. 
  6. ^ Other sources give 305 mm at 1000 meters, 90°.

References