A guy gave me some old ammo for my Garand . It was pretty tarnished and ugly . I put it in a tumbler and it cleaned up pretty good .
lucky it didnt hit on the primers
I've yet to hear a confirmed story of live ammo touching off in a tumbler.
That said-- I still don't do it.
Unless there is a build up of tarnish or corossion, the best thing to do is shoot it. If you are worried about it sticking in the chamber, squirt some CLP or light gun oil on it, roll it in a towel to clean off the excess, then shoot it.
lucky it didnt hit on the primers