So I just bought a used M77 and I'm having issues getting it to chamber various rounds. I was at my reloading bench and was just grabbing a few various empty sized cases that I had full length sized for another gun and I couldn't close the bolt. I was able to chamber some loaded rounds that I had loaded for another gun and they chambered normal. All of my sizing is full length so I wouldn't think the rounds loaded for another gun would be an issue. And for what its worth, the cases that I seem to have nearly all the trouble with are Norma. Rems, Frontier and WW seem to be less troublesome. So is this a case of this particular M77 having a tight or short chamber or?