I fired my new to me model 70 today. And the bolt had a catch in it about 3/4 the way up. I can reinsert the fired case and it will still catch. It did this with one load but not the other. The load in question is 375 h&h 300 grain Sierra with 74 grains of IMR 4350. This is not near maximum and give about 2480. It was also six degrees today. The primers are cratered a bit but not bad. Is this a pressure problem or something else?