Getting back to the original post . . . .
There was no case separation. It was just mentioned by a shooter that considered associating case separation to this symptom. A short bullet in the long throated Weatherby rifle is a very good theory.
However, I have this pisture on my website that shows a 300 Wby, a 300 Win Mag, and a 300 Win Mag case that was fired in a 300 Wby rifle by mistake. There were no case dents there. The shooter didn't examine his fired cases until he fired 3 or 4 rounds, and none of those cases had dents either. Surely this situation had a rather long jump to the rifling. (By the way, don't try to duplicate this shooters mistake!)
Do I still believe that the cause is irratic powder detonation? . . . . yep.