[Linear Thinker]

With all due respect to a professional ballistician posting here, I've had a bad experience tumbling loaded rounds.
About 20 years ago, Paragon (late and unlamented) imported a large quantity of Brit 308 ammo, marked RG67 (Radway Green 1967), which they advertised as like-new and shiny, selling for ~11 cents apiece.
Well, my lot of 5000 wasn't. All of the rounds were tarnished.

I took about 100 and vibra-tumbled them for 2 hours to get the crud off the cases. The rounds looked much nicer after the tumbling.

Took them to the range with my HB FAL, the first couple of rounds fired fine. The next round made an odd noise, and the action locked tight. I was unable to open the action on the range. After getting the rifle home, I was able to take everything apart. The brass case exploded (for lack of a better term) inside the rifle, the brass extruded into openings and jammed everything. No permanent harm to the rifle, a testament to good design.

I pulled the heads off some of the remaining tumbled rounds. The powder inside has partially turned to reddish dust, mixed in with extruded powder. I compared those to un-tumbled rounds, no such disintegration. Needless to say, I discarded the tumbled rounds.

My take on the above is that the extruded powder inside has partially disintegrated as the result of tumbling.
It may have been because of age or improper storage.
Whatever the cause, the burning rate of tumbled powder has changed dramatically. It was probably closer to burning rate of a pistol powder, not medium-speed rifle powder as is needed for .308, with corresponding astronomic pressure.

I will never tumble loaded rounds again, and recommend you don't either - unless you get a thrill from the risk of a hand grenade going off in proximity to your face.