Development started in October 1942, due to a
General Staff order for a successor to the
17-pdr gun. Basic requirements involved the new gun to be "at least 25% more effective" than the 17-pdr. Initial focus was on development of a 55-pdr gun, although advancements in 17-pdr ammunition meant the advantages that would be secured by the 55-pdr were no longer as desirable, while the 55-pdr would suffer from considerable disadvantages such as the difficulties in the handling and stowage of ammunition. Other options considered included a 76 mm (3-inch) 17-pdr firing a
Armour Piercing Composite Rigid (APCR) shot at a
muzzle velocity of The
QF 3.7-inch anti-aircraft gun was selected as the basis for the 30-pdr anti-tank gun in September 1943 and for pilots to be built. During development, it was proposed that a shot would give better performance, and this new design was trialled as the QF 37 pdr EX1 in June 1944. Following firing trials, the 37 lb shot was dropped for a shot, and the gun was accepted as the QF 32-pdr. At least one 32-pdr was developed as an anti-tank gun on a wheeled carriage and a single example using a novel form of muzzle brake was installed in a
de Havilland Mosquito FB Mk. XVIII as an up-gunned version of the 'Tsetse', in place of the 57 mm 6-pounder
Molins gun. While flight trials did not take place until after the war had ended, the aircraft flew and the gun fired without problems. The 32-pdr fired a 32 lb (14.5 kg)
armour-piercing shot at a muzzle velocity of and a
Armour-piercing discarding sabot (APDS) shot at . During firing trials on 28 June 1945, the 32-pdr Shot Mk.3 APDS shot penetrated of
rolled homogeneous armour at 50° – a line of sight equivalent of - and on impact, which meant that its penetration surpassed those of the 17-pdr and
20-pdr APDS rounds, and could even rival early
armour-piercing fin-stabilized discarding sabot (APFSDS) rounds in raw penetration. The 32-pdr gun could have easily penetrated the front hull of the
Tiger II (
Konigstiger) and
Jagdtiger; it would have been the only allied anti-tank gun that could do so in the Second World War. By comparison the M308 HVAP shell of the
90 mm M3 anti-tank gun on the US
M36 Gun Motor Carriage could penetrate at 50° at . Development was halted with the end of the war: the 17-pdr was replaced by the 20-pdr for tank use, and by the
120 mm 'Battalion Anti Tank' recoilless rifle as an anti-tank artillery weapon. For infantry use it was intended to replace the 17-pdr with
anti-tank guided missiles. ==Ammunition==