Tumbling primed brass

[joe-nwt]

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In general, when safety is a concern, you should assume worst case, so I don't tumble live rounds. And I won't until someone explains to me the flaw in the model described above.

So which is it, a model? or fact as you seem to have described in your first post on the matter?

Tumbling a loaded round, especially one where the powder doesn't fill the cartridge, can cause the powder to break down into a finer particle size. This can significantly increase the firing pressure, with obvious implications for safety/reliability.

BTW, if we are repeating what others have said, I've heard more than once that the factory tumbles loaded rounds to polish them up before packaging. That sounds plausible also, yes?

 

[ajarmst]

Hey, your rifle, your rules. I don't have a lot invested in being right on this. I choose not to.

I must confess to a bit of amusement that---in a forum where people talk about sorting brass by weight, measuring charges to the tenth of a grain, neck turning, and measuring jump to the hundredth of an inch---I'm being taken to task for recommending against tossing a bunch of rounds into a bucket and then shaking them.

 

[joe-nwt]

Hey, your rifle, your rules. I don't have a lot invested in being right on this. I choose not to.

I must confess to a bit of amusement that---in a forum where people talk about sorting brass by weight, measuring charges to the tenth of a grain, neck turning, and measuring jump to the hundredth of an inch---I'm being taken to task for recommending against tossing a bunch of rounds into a bucket and then shaking them.

Hey, well the OP didn't ask if tumbling would improve accuracy, now did he? I'm not taking you to task. Just don't want you scaring the newbie's, that's all. I like to present facts and some personal experience and then let them decide what's safe, even tumbling live rounds. For what it's worth, I don't tumble live round either. Could never see the point.

 

[climbhigher]

HA HA, Thanks everybody. I think I will just load em up and shoot them. I will wait for a day when nobody is around to see my tarnished brass!

 

[Scar270]

Very interesting. I actually have another tumbler here that's not doing anything. Perhaps I should dedicate it to the purpose and not worry about changing media. How many rounds do you tumble at once, and how much mineral spirits do you use per batch?

The mineral spirits don't bother the primers?

Probably about a capful of mineral spirits, so maybe half an ounce. Doesn't take very much. Start low, if it's not doing the job add a little bit.

I can do about 200 45acp, 300 .38 spcl, give or take. If you get too many in the tumbler can't vibrate any more and just shakes. I know mine can't handle 400 .45 acp, I tried that once.

I've had no problems with ignition so far after tumbling loaded ammo with mineral spirits on the media, I've fired several thousand that way so far.

 

[Scar270]

I'm sure it's more CYA than anything else -- but the fact that tumbler manufacturers care more about not being sued than whether you blow up your gun or not doesn't make the warning wrong. I do admit that the only "empirical" evidence I've run across for over-pressure due to powder break-down are the anecdotal "I know I guy who knows a guy who..." type that I tend to ignore.

However, I also know that smokeless powder granules will fracture under friction and that subjecting material like that to a lot of collisions (as is going to happen in tumbling) will cause it to break down somewhat. I also know that, other things being equal, powder in flake form will generate gas faster than in rod or ball form (fracture is much more likely in large particles, and they have more mass in collision), and that finer particles will generate gas more quickly due to more surface area. This supports the idea that tumbling powder could cause it to generate finer particles, and potentially more pressure. Now, obviously, this is going to have a lot of variables -- I expect it would be less of a concern for ball powder than rod, and even less for flake. It would also be less a concern in cartridges that are full or nearly full (so the mean path between collisions is very small), etc.

In general, when safety is a concern, you should assume worst case, so I don't tumble live rounds. And I won't until someone explains to me the flaw in the model described above.

For sure if the powder breaks down, it increases surface area and burn rate. We've known that for centuries with black powder, fffg burns faster then fg.

However the question is whether the powder breaks down by tumbling live ammo, I don't know anyone who has tested this theory in real depth, but anything I've read from people who have tried to collect empirical evidence is there is no change in the ammo performance after several days in a tumbler. Anyone who advices against it has no studies to show that the powder does break down.

Again if I tumble loaded ammo to get the case lube off, it's maybe in the tumbler 5-10 minutes, and if I tumble it to get the Liquid Alox off, it's probably 20 minutes to maybe 30 minutes tops.

I too have heard that factories tumble their loaded ammo, but I have not been able to confirm that myself.

 

[Skyhawk]

Probably about a capful of mineral spirits, so maybe half an ounce. Doesn't take very much. Start low, if it's not doing the job add a little bit.

I can do about 200 45acp, 300 .38 spcl, give or take. If you get too many in the tumbler can't vibrate any more and just shakes. I know mine can't handle 400 .45 acp, I tried that once.

I've had no problems with ignition so far after tumbling loaded ammo with mineral spirits on the media, I've fired several thousand that way so far.

Thanks, I just gave it a try and learned a few things. First doing this in a Frankford Arsenal Quick-N-EZ tumbler does not work. The rounds just drop to the bottom of the bowl and vibrate against the plastic pretty violently. That worried me. Nothing circulates, even with only 200 9mm.

So I decided to switch the media in my Ultra-Vibe 18 Thumler's and give that a go. What a difference. It took 400 9mm easily and circulated them fine. 10 minutes is all it took to get the bullets shiny clean with just a capful as you suggested.

So I've just reminded myself why the Frankford Asenal is gathering dust under the work bench. At least I can say I've used it twice now. (It's my backup just in case something happens to the Thumler's.)

 

[Scar270]

Excellent. I should maybe add that the reason I find Corncob works best, is the Walnut is finer and sometimes some of it will stick to the bullets if there are sharp corners, such as on a wadcutter, or up against the case mouth.

 

[Skyhawk]

I'll report back after trying them at the range tomorrow. Like every new load recipe I concoct, I'll have the wife shoot them first out of my cheapest gun while I hide safely behind the side berm.

*kidding*

 

[Skyhawk]

Well we fired all the tumbled 9mm at the range today and there was no detectable change in pressure or ballistic performance. I didn't crono them, but they felt like the same powder-puff loads one would expect from driving 130gr LRN with 4gr of W231. Sadly tumbling did not improve my accuracy

I'll probably not continue to tumble the loads because I don't see that the benefits are really worth the extra work. Sure they look nice, but I lube pretty lightly with the LLA and let it dry for days so it's not that much of a problem.