Incidentally, when P.O. Ackley did that test with the .30/30, it was with quite a bit higher pressures than a standard .30/30, as he was demonstrating the sick-to-the-chamber walls phenomenon of the Ackley Improved case design with blown out sides and only .020 taper overall, only .010 per side.

A grossly tapered case will still produce lots of bolt thrust, but a dry case and dry chamber is so much better than oiled ones.