I believe I had that problem once. Turned out to be the extractor. Fought the resizing die for awhile. As a test I put a different bolt in it it chambered fine. Changed the extractor all was well. Hope this helps.
Yep, I also had one rifle that wouldn't chamber a particular brand of brass, it was just a hair greater in diameter or rim thickness, can't recall which, but one of those was the why.
