brayhaven,
Ackley never fired factory .30-30 loads in a STANDARD chamber with exceess headspace, so we have no comparison about how they might have backed up either. But I have seen it hundreds of times when shooting various low-pressure cartridges from the .25-20 to .348 Winchester.
I have yet to see a .30-06 (or similar pressure cartridge) leave primers backed out with normal pressures. They will with "starting" or reduced loads, but there isn't a .30-06 case made that won't stretch enough to back over the primer at normal pressures. In fact I have thousands of fired factory cases from higher-pressure ammo in my shop, and none show backed-out primers. The ONLY ones that do are .25-20's, 25-35's, .30-30's, American 8x57's and similar low-pressure rounds.
In fact, that's the very reason "flattened" primers aren't always an indication of excessive pressure, as so many assume. When a high pressure (say 55,000 PSI) round is fired in a chamber with a little extra headspace, the primer backs out and, if pressures are high enough, expands slightly, because it's no longer supported by the primer pocket.But then the case backs up over the expanded primer, "flattening" it, even when pressures are normal.
Please note that the mention of lubed cases not expanded to fill the chamber specifically applied to SOME oils, not all.
The experiments with bolt-face pressures in the article were repeated many times, with cases of various shapes, and the result was always the same, no matter the case shape.
But apparently you made up your mind about all of this a long time ago.
