Short chamber on that rifle. This is the reason I don't jam bullets I the lands I've seen it and had it happen several times.
I had it happen about 25 years ago while hunting. I had shot a doe with my 338 win mag and cycled another round. When I got back to the truck the bolt wouldn't budge. I had 200 gr BT bullets loaded to kiss the lands and I think the recoil may have caused the bullets in the magazine to move just enough out of the case neck to jam the lands.
Finally turned the bolt and powder dumped out in the action. Luckily I brought a second rifle with me.
