The 76.2 mm 17-pounder AT gun was the perfect successor of the 6 pdr.: very powerful, easy to conceal and with a very good range of fire. It can pierce the heaviest armor, and though useful its high production. The 17 pdr. gun can therefore only be deployed at key locations, and requires infantry for protection and reconnaissance to make the most of its capabilities.
Before the QF 6-pounder had entered service, the British predicted that it would soon be inadequate given the increasing armour of German tanks. In late 1940 design of a replacement was started, and was largely complete by the end of 1941. A prototype production line was set up that spring, and with the appearance of Tiger I tanks in North Africa, the first 100 prototype 17-pdr anti-tank guns were quickly sent off to help counter this new threat. So great was the rush that they were sent before proper carriages had been developed, and the guns had to be mounted in the carriages of 25-pounder gun-howitzers. These early weapons were known as 17/25-pounders and given the codename Pheasant. They first saw action in February 1943. Fully developed 17-pdrs started production in 1943 and were first used during the Italian Campaign.
The 17-pdr outperformed all other Allied armour-piercing guns, and was quickly adapted for use on various tank chassis. However, few tanks were capable of carrying such a large gun due to the limitation of the size of their turret ring. It was expected that a 75 mm gun under development by Vickers would be used for tanks, but this did not enter service. The British had plans in hand for a tank - based on the Cromwell then under development - to carry the 17 pounder. However the problems inherent in the modifications meant the result, the Cruiser Mark VIII Challenger, was delayed and relatively few built.
However, the British devised a conversion for their US-supplied M4 Sherman tanks to take the 17 pounder and it was rushed into service in time for D-Day as the Sherman Firefly. The gun (a modified design was produced specifically for the Firefly) had to be rotated through 90 degrees to fit into the turret of the Sherman, i.e. it lay on its side, and an additional box was welded to the back of the turret to take the radio which was moved to allow for the breech and its recoil. More Shermans were converted until about 50% of Shermans in British service were Fireflies. 17pdr SP Achilles of the Battle of the Bulge in La Roche-en-Ardenne.
The British also converted some of their US-produced M10 tank destroyers, replacing the 3-inch (76 mm) cannon with the 17-pdr; the resulting vehicles were called Achilles or just 17 pdr M10. The 17-pdr was also successfully fitted to the Australian-designed Sentinel tank during trials, though no Sentinels equipped with this gun entered service with the Australian Army. The 17-pounder anti-tank guns saw action in Korea, against tanks and in general support use against bunker positions. Afterwards, it was largely replaced in the tank role by the Ordnance QF 20 pounder and in the anti-tank role by the 120 mm L6 WOMBAT recoilless gun. The United States Army did not use the 17-pounder in action, though the gun was offered to US forces with a number of Shermans modified for testing.
Large cal. AP shell