This has been batted around on some of the other forums. The major ammunition manufacturers tumble their ammo after it has been loaded and before they put it in the boxes for sale, so for them, it appears not to be a problem.
I accidentally tumbled a live .38 Special round in my rotary tumbler and it shot just fine.
Granted, if you rotary tumbled something long enough, the powder might break down slightly and the burn rate might change.
If you're talking about a vibrating tumbler, it should not be a problem.
Yes I still do. Powder come in different forms with different burn rates. I'm sure the manufacturers know what they are doing, but regular guys don't. Hell you take a slow burn rate tumble it & it becomes a fast burn rate then what? Do you really want to seize up a gun? Blow up a gun?.
I've shot some really grimy surplus mostly out of Evil Black Guns over the years with no problems. If the ammo was that nasty that your afraid it wont chamber or eject you must have a gun with a vary tight chamber why risk it.
Ever think about the ammo that old cowboys had on their gun belt loops out in the weather & becoming green from reacting to the leather? You think that was their concern?
You can do what you want, but I would never do it personally.