Back during hunting season a Browning A Bolt in .270 Winchester was brought into the local gun shop with the bolt locked up. The gunsmith tapped the bolt handle back and forth with a rawhide mallet until it turned loose. The cartridge case was welded to the bolt face, and required considerable force to remove it. Only about 1/3 of the headstamp was left, and the primer pocket was approximately double it's original diameter. On the A Bolt, the cartridge case is almost totally supported, but the approximately 1/16" just ahead of the extractor groove that is not supported had expanded to look like a mini magnum belt. The cartridge was the first one out of a new box of Remington .270 ammunition. The owner of the rifle was going to send the remaining box back to Remington, but I never heard the outcome.
Just goes to show that just because you are using factory ammo you are perfectly safe. Had the ammunition been shot in a rifle that did not support the cartridge case like the Browning, the results would have been distasterous.