brayhaven,
Ackley's tests were deeply flawed. More recent tests, with better testing equipment (including pressure-sensitive taper used in a number of industrial applications) indicate case shape has zero effect on "breech pressure"--the pressure on the bolt face. This is because at pressures above .30-30 level cartridges brass stretches, and overall chamber pressure is distributed equally to the bolt face. Extremely heavy-walled cases might prevent this, but not many commercial cases are heavy enough to prevent stretching at 60,000 PSI.
