The QF 6-pdr was the highly successful replacement for the 2-pdr; being copied by the Americans as the 57mm gun; M1. Its useful lifespan was extended by new developments in ammunition that improved its armour penetration capabilities; allowing it to knock out Panthers and Tigers from the flank.
Although supplemented by the 17-pdr; it was never entirely replaced and continued to serve in infantry units long after the war ended. The 6-pdr replaced the 2-pdr as the standard weapon in British tanks as it became available; but even as it did so; a replacement was being sought. Although HE shells were available; the limited size of charge meant they were relatively ineffective; making the 6-pdr less than ideal as a tank gun and leading to the development of the 75mm weapon used in British tanks such as the Cromwell and Churchill. The QF 6-pdr used by British airborne forces had a special carriage that allowed them to be towed as if they were light anti-tank guns.
