75 mm Turret Mounted M3 Grant and New Research

The_Chieftain: I'm looking at where the breech is in that proposed cut-away drawing, seeing how close it is to the turret ring (which is about 10% smaller than the M4's turret ring) as well as how close it is to the rear turret wall, and trying to figure out how there is enough room to line up a 75mm shell behind the breech in order to insert it into the gun. I'm not seeing it.