You mention a topic that is very interesting to me. Tumbling loaded ammo. I agree with you on the safety issue to some degree. I only shoot SWC bullets so I'm not really worried about a spitzer bullet hitting the primer. Actually, I personally doubt that even spitzer bullets would cause a problem. (NOTE- for anyone reading this I am not saying that you should tumble any ammo)
I have done some *limited* testing of tumbling loaded rounds. About 6 different powders and caliber combinations. I only have a Chronograph to compare results with. But the bottom line was that after up to 1 hour in a tumbler the loaded rounds showed NO increase in MV over the untumbled rounds.
Have you ever read of (from an authoratative source) or had personal experience with tumbled rounds causing pressure problems ?