Funny story about 8mm and 30-06: I’ve actually found range brass before that was 8mm fire formed in a 30-06 chamber. I did some research and found that it’s not unheard of, and under the right circumstances shoots ok (Not saying anyone should- ever!)
With light loaded U.S. commercial ammo using soft lead cored bullets, the smaller capacity round fire forms to the larger chamber. This would normally result in lower than normal pressures except that it’s squeezing a relatively soft .323 bullet through a .308 hole. Scary as heck but not necessarily kaboom.
Try that with a full power surplus 8x57 round, especially steel core, and I would fully expect guaranteed destruction.