I've seen a couple of fired cases from a .30-06 that had a ragged edge at their shoulder where the neck broke off and went down the barrel with the bullet. Yes, the case heads had extruded well back into the bolt face cutouts and the primer was well mushroomed out of its pocket and even the dimple from the firing pin was barely visible. Lots of force on the back end of that case. Didn't seem to hurt that old Winchester 70 bolt or receiver.
Inspection of those many-year-old handloads showed the corrosion from dissimilar metal contact(copper bullet jacket against brass case neck) had bonded them together. The force needed to get the bullet and the case neck out of the chamber was enough to break the case neck off the round. First thing the ammo owner tried was to break the bond between bullet and case mouth by seating the bullet deeper. That resulted in pushing the shoulder back into the case body. He trashed the rest of it.