Experience with the US M3 75 mm gun suggested this thinking was wrong, that a single gun could be used in a "dual purpose" role against both tanks and softer targets. This led Vickers to begin development of a 75 mm weapon of 50 calibres in length, which would fire the same HE shell as the US gun, but with a higher propellant load that would make its anti-tank rounds more effective. However, as examples of this weapon began to arrive in May 1943, it was clear it would not fit into any turret that could be mated to the Cromwell's turret ring.