I don't know the exact barrel diameter of a 32 acp and a 7.65mm (in comparison) but I wonder if the area where the rounds go is sleeved, like the chamber adapter that changed a 30-06 to 308 by fire forming / fitting with either epoxy or by tightness?
Ed
looked it up
32 acp
https://en.wikipedia.org/wiki/.32_ACP
Bullet diameter .3125 in (7.94 mm)
7.65mm
Bullet diameter 7.85 mm (0.309 in)
so, it sounds to me that it could be 'bored' out a bit and just the bore sleeved?
Other thoughts?
Rich?