Join the resistance in an alternate reality where the allies lost WW2 and...
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 heavy tanks from the flank.
At the outbreak of war, the QF 2-pdr was the standard anti-tank gun of the British Army. It was an adequate weapon for the time, being slightly more effective in terms of armour penetration then the contemporary German 37mm PaK 36.