Thought I might post this and see if anyone has any problems like this
The owner is has a 770 in 300WM that when fired the bolt will not lift or is extremely hard to open, if you wait a couple of minutes it opens much easier. This is with factory ammunition.

Rem 770's and late model 700's are notorious for sticking cases with the Mags. Rough chambers are the issue. Check fired brass for hazing and tool marks. You will need to polish the chamber with 600 grit on a split dowel. In the shop, we use a section of an old aluminum shotgun cleaning rod. The tip of the rod is tapered to match the chamber shoulder. Split the rod with a hack saw. Wrap a strip of 600 grit around the dowel using a cleaning patch between wraps. Adjust the wraps until you get a nice tight fit. Spin it with an electric drill motor. Move the polisher in and out. 15 seconds ought to do it. Then, oil the paper and do it again.