Hmmm . . . they generally warn against using, say, 3" shells in a 2 3/4" chamber because of a pressure spike when the crimp unfolds into the bore - not the chamber. With cut shells the whole forward end of the case - not just the crimp - goes down the bore.
The chamber volume will increase a bit lowering pressure as the forward part of the shell moves . . . but this is another experiment I won't be doing with any of my guns.