This is from an old thread on: Is it Ok to polish live ammo in a tumbler? - THR
So at least one (and I think most likely, all) manufacturer(s) polish loaded ammo.
September 19, 2005, 10:14 PM
I can attest that we too have been tumbling live ammo for about 30 years, without incedent. There has been an issue on a decapping machine once, before I was even born, and of course you can't avoid the occasional primer pop in an ammo load when you run millions of rounds a year. We tumble litterally millions of rounds a year, live, without incident.
You have to of course tumble them with the proper amout of product, walnut shell, corn cob or what have you. If not, you may end up with more tiny dents in larger cases (45-70) than you would like.
Remember that rounds like 9mm and such have a small volume inside the case the ISN'T filled with powder. Powder is SO light and HARD that I could not possibly see it breaking itself down with just a slight area to move in. I mean, you would probably have to shake a half full keg VERY hard for quite a while to develop a sufficient amount of wear on the powder to matter.
I suppose if I HAD to worry about something, it would be with a long grained powder. The would tend, based totally on physics to break more easily than a typical ball powder. Obviously if one grain struck another right in its center with its own tip, it would potentially have enough of a 'lever arm' to snap the other grain.
I would say, if you are tumbling slowly enough, with enough 'polising compound' you will be more than fine. No need to be turning ammo at 1800 RPM if you know what i mean!