I had the same problem with a 7MM Rem Mag. Back in the day when I wanted EVERYTHING that rifle could deliver, I was loading it right up to the edge. Fortunately, it was a Browning Safari Grade. I had a primer blow out and had to beat the bolt open with a rubber hammer. Didn't hurt that big Mauser style action any though.
I pulled all the bullets and backed the load down a couple of notches.
Wish I still had that rifle. It was stolen along with some other really neat old family gun stuff when I was in 'Nam. Even though my "magnum love" days are long gone, that was a sweet rifle.
Oh well.