The M-4, named General Sherman in UK under Lend Lease, was 'designed' in about three months largely by redesigning the M-3, designated as General Lee (with US -pattern turret) by the British Army. The 75mm gun was mounted for two reasons: it was in production, and there was ample ammunition available for it. There was an urgent need for better tanks than the M-3 Lee/Grant in North Africa.
It isn't much good to put a weapon into a tank that hadn't actually been tested. Testing of the M1 gun identified that the turret needed a counterweight, requiring adoption of a different turret design to that of the M-4 initial production.
It isn't much good to put a weapon into a tank that hadn't actually been tested. Testing of the M1 gun identified that the turret needed a counterweight, requiring adoption of a different turret design to that of the M-4 initial production.
Of course in Traveller highr TLs the modelling and simulation technology would allow for a design process that gets all engineering right from the word Go 