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.
I would respectfully disagree with those conclusions. My 45 years gunsmithing & shooting show the opposite. In fact with a dry chamber and cartridge case, there is very little pressure on the bolt face. Proof of this is easily seen in rifles with excess headspace. If the case & chamber are not oiled, the primer simply backs out against the bolt face. It's one reason headspace is not as important in regards to safety as some would have us believe.
If the case were hitting the bolt face, the primer would be flush. Stretching occurs in the area just ahead of the case head and forward.
The minimum body taper reduces the likelihood of thrust in a clean oiled environment. And the 30/30 AI loads he used were much higher pressures than factory. He always offered to shoot the 30/30 AI in a 94 win with the locking lugs removed to prove his point. Never heard of anyone taking him up on it though :o).
