bdotson;
Not to argue but it is not uncommon, I have 2 chambers that do the same thing, @ 34 grains it is compressed, I can get 34.4 max and no more in the case. I use my own 118gr/ 1 inch jacket bullets, H 4198 powder, Lapua cases with a .330 neck, .324 neck bushing and the chamber is Robinette throated for 1 inch jackets, I own the reamer and the die reamer; the cases are bumped after every firing. I do my own chambers, make my own dies, everything is lapped to my liking so things fit. I have Redding dies for the 30BR but never was able to make things work well; the Wilson seater would be a better option for this cartridge. IMO………
In order to get a good grip on the bullet the cases must be annealed after 3-4 firings, the .324 bushing just gives insurance that they stay put. If you are not using a drop tube and a slow fill the 34 grains will be at the case mouth. A .325 bushing size will work well until the brass gets stiff, when this happens you either drop the bushing size, anneal or the third alternative is make new brass. I find it much easier to anneal than make new brass but each to his own.
This all hinges on your chamber, what reamer it was done with and who did it, all things are not equal.
The above is my past experiences with this cartridge; I put this out here for reference to your question.
Rick