Had a range session with a few of my shooting companions this weekend. After the shoot, we were indulging in a few adult beverages and the conversation turned to brass preparation, nobody's favorite past time! And then, one of the old boys said he'd had to tumble some live rounds that had gotten "moldy" in storage. There was a loud gasp, and we checked the guy for fingers and eyes and ears, and they were all there. We really started in on the guy about the safety issues associated with tumbling live rounds. He said he's been doing it for years and never got anything but shiny brass out of doing it. What say you folks? I've been told since I was a puppy that you should NEVER tumble live rounds.

Well... I mean... it's not something that I would do. In fact, until you just mentioned it, that particular task has never actually crossed by mind once - maybe because I've never had moldy ammo. That said, and now having thought about it for awhile... while I still wouldn't do it personally, I don't think it's actually that risky. I mean, setting off a primer in the tumbler doesn't seem horribly likely and exploding ammo outside of a chamber isn't really that dangerous in itself. Being lit off outside a chamber, it just kind of explodes more like a firecracker than anything else and doesn't really yeet the projectile at super dangerous speeds normally...doubtful at any speed that would penetrate the tumbler plastic. A round going off shouldn't cause any serious pressure issues within the tumbler itself ... I think in the rare instance where you actually set off a round, other than scaring the crap out of yourself if you are near it, the worst that will likely happen is you damage your tumbler.

I would stick with the 'Don't tumble live rounds' position... at the same time, I don't think your friend is in any serious risk of serious injury either.

All that said, you'll never see me knowingly put a live round in the tumbler LOL

Out!

Although I’ve heard of many doing it with no issues. For me it would have to be 100s of rounds to consider it.

I know people that have but never have done it myself.

Can’t say I haven’t done it. Not on purpose but just recently a friend gave me a plastic bag with a 100 or so once fired 6.5 Creedmoor brass. I just dumped them in a tumbler and turned it on.
Once I removed there was a live round included. Seems fine will eventually shoot it just to see if there is any changes.
Really how much difference is that from putting 50 rounds in an MTM container and driving out west hunting down gravel roads etc for 15 hours or so?

I've done it MANY times. I use vibrating brass cleaners, and not tumblers. Vibrating cleaners I see no problem with it. An old rotary tumbler, maybe could have an issue. But it takes a lot of force hit a primer just right for it to go off.

The main thing I would worry about is the tumbling/vibration shaking the primer mix compound loose inside the primer causing a faulty primer.

I've heard of guys leaving a box of ammo in a glove box for many years on end, traveling rough terrain and subjecting the ammo to a ton of vibration long term. When fired, no discernable difference due to that treatment was noted.

I think keeping loaded ammo relatively cool and dry in the first place is probably a better approach than tumbling it after it starts looking like it was found in a dump!

Chad, my "tumbler" is a Hornady product, and it just sits there and vibrates, with no tumbling action at all. I don't currently have any live rounds that need to be buffed up, but it's good to know that the danger is pretty remote if using a vibrating rather than a tumbling brass cleaner.

I've never done it but I would...as Chad said, it takes a whole lot more than people think to set off a primer. I've got some I need to post a picture of because I had a firing pin spring lay down and it won't set them off.

I always though the danger of tumbling live ammo would be related to the powder, not the primers. My own concerns have related to the coatings on powder kernels rubbing off, or the kernels breaking up into finer pieces resulting in altered (and presumable faster) burn rates. I've seen a lot of questions and discussion about decapping live primers and trying to render them inert for various reasons. Surprising conclusions emerge sometimes.

I was always afraid but tried it and could not tell any difference in the final ammo performance. I had some loaded .308 that would fit 3 guns but not a tight Tikka chamber. Had to run them through a body die to get that last little bit sized. Lubed them, sized them, tumbled them, and shot them. No difference in accuracy or operation in a gas gun. Powder was IMR3031 which is a stick and I thought it might break the powder down to a fine dust but after pulling a bullet it looked just like new powder.

Dont tumble hollow points fills up the cavity and can really pack it in and removing it can be difficult.

I have done it for years in 3 or 4 different brands of vibratory tumblers with media. Never an issue.

Surprise! I have done it with .357 Magnum in a Lyman corncob vibratory machine. Never did it again because it makes cast bullet loads ugly. The lead turns dark grey. Might try it with 5.56 as it's the one I use jacketed bullets for. When a cartridge "goes off" with no chamber or barrel, there is hardly any umph behind it ... and the chances of one going off in a tumbler is so remotely low it's basically the same odds as one going off in the chamber of a carry gun in your console.

***EDIT to add: I have successfully de-capped live primers and reused them before. Also not a big deal in my opinion.

I am pretty sure that almost all factory ammo is ran through a vibratory cleaning process before it it boxed up and shipped out. I have on occasion used my vibratory cleaner to polish up some ammo that wasn't pretty enough for my rifle, LOL.

I will have to look, but I came across an experiment online where they loaded non vibrated loaded ammo against ammo that had been tumbled for 8 hours. They saw no powder or velocity degradation between the two.

I have been reloading for over 50 years and have had at least four different tumblers and have tumbled several live rounds with no problems. I would worry more about loading a lever action with LEVERevoltion ammo with bullet tips against the primers than tumbling live rounds.