I don't really understand what they did to manage to avoid the need to adopt the bigger T23 turret......
As I understand it, it was nothing phyiscal, just a matter of perspective.
In 1942 and early '43, you don't have a specific need for the 76mm gun, but rather an
anticipated future need for the gun. And you have to remember, US Ordnance is basically
only considering the US Army's needs when they're developing new equipment. So when they put American troops in the turret and they complain about the lack of room to handle the larger ammunition, then the
potential advantages of the extra penetration didn't seem to be worth it when weighed against the poorer HE effect (remember, that was the primary role and ammunition type used by US tanks during every stage of WWII), slower rate of fire, reduced ammunition capacity, and additional supply chain concerns. It wasn't an impossible fit, it just wasn't considered worth the downsides.
http://the.shadock.free.fr/sherman_minutia/turret_types/76mm_turrets.htmlAnd they didn't specifically develop the new 76mm turret in response to these complaints so that the Sherman could mount the 76mm gun, but it was just that the new, larger turret developed for the T23 tank (Ordnance's replacement for the Sherman) had the same turret ring as the Sherman. By mid-1943, when the 76mm was reconsidered for the Sherman, 250 T23 tanks had been ordered and more orders were expected, so it wasn't a theoretical, paper design. This was a turret that was designed & developed, the castings existed, and the turret was already
in production, so it was basically a drop in replacement that would just require changes to the hull ammunition racks.
http://the.shadock.free.fr/sherman_minutia/m4a3e4/m4a3e4.htmlNow, after WWII, the equation is much different. Tank armor is getting thicker, not thinner. The 76mm gun has proved its worth and nobody wants a warmed up WWI French 75 anymore. We're not talking about making new turrets and new tanks. We're talking about making the most efficient use out of existing parts.
We're not worried about the US Army, these are only meant for export. We're not worrying about bulky American troops in the turret, complaining about being too cramped. We're talking about taking 100 tanks, sending them on a boat across the ocean, and never having to think about it again. You're not worrying about US Army doctrine and stepping on the shoes of the Tank Destroyer Command. These tanks could very well be the only tanks in the inventory of the MDAP recipient army. In that world, then squeezing the 76mm gun into the 75mm Sherman turret is just fine.
The British came to similar conclusions when they developed the Charioteer on converted Cromwell chassis after WWII. That was even tougher. They had to design a new turret entirely and still chuck one guy out of it to make the bigger gun fit. By comparison, the M4E6 compromise was great.
Cheers,
Logan