I have tumbled live rounds for years to remove bullet lube. Don't plan to change. I keep one of my tumblers filled with shredded egg carton cardboard or rags torn up in inch squares just for this purpose. When you shoot a few hundred rounds a week at prairie dogs you learn how to speed things up.

I've read threads like this with interest since I got my first puter 6 years ago. I find it humorous that guys can matter-of-factly state that one shells bullet hitting anothers primer could "set it off"! How in tarnation can tightly packed shells in tumbler media get enough momentum to hit a primer hard enough to set it off? To say nothing of the fact that the soft lead nose of a bullet couldn't dent a primer. Maybe a FMJ or bronze tip might be able to do it, but it still lacks enertia to hit hard enough.

As far as degrading powder goes, did you ever try to crack a kernal of powder? It's some tough stuff. Coatings may be worn off over a long time frame, but enough to destroy a gun?

I just recently started tumbling live ammo. I needed to remove the lube after loading in my new dillon. Using new corn cob media it only takes 5-10 minutes in my midway vibrator.

I would not tumble live ammo - The powder could be broken down into a finer powder. If you think of what happens when burning something - if you break/grind it up into smaller pieces it will burn faster. In a firearm this could lead to higher pressures. I would not attempt doing this or even recommend trying it. This adds a variable that would be difficult to monitor (other than pulling bullets & checking if the powder is still ok) and control.
In my opinion don't do it. It could cause harm to the person shooting the ammo in the worst case.

This is a perfect example of something that the possible dangers far outweigh the benefits. A little time saved is simply not worth the risk, there are other better ways to get shiny new brass. You can remove dillon case lube from cases by tossing them on an old towel and rolling around faster than you can tumble them. Old military rounds can be polished with steel wool and the case held in a lee case trimmer etc.. There's no good reason to save a few seconds by risking blowing up a firearm or a tumbler. It's simply a very bad idea to tumble live rounds........DJ