What is this rash on these cases?

[boisepaw]

I bought over 100 6.5 CM cases from a guy without looking at them. Just a bunch of cases in a bag. They had been sitting in his garage for a couple of years after initially being fired out of an AR-10.

I tossed 'em in my vibratory tumbler and when they came out they were all nice and shiny except...90% of them had this rash on them to a greater or lesser degree. I tried scraping it off with my fingernail and washing it off and even tried a little steel wool. But to no avail.

Any idea what I'm looking at? Just plain old corrosion?

Any options other than tossing them in the garbage?

 

[AlBeight]

I’m having a difficult time equating “90% discolored” with “all nice and shiny”.

Seems they came out “90 % all shitty” with 10% being “nice and shiny”?

 

[4g64loser]

Wet tumbler or ultrasonic might work. I've cleaned up some pretty funky brass in my wet tumbler before.

 

[erwos]

Wet tumble with pins would probably clear this up. I have mostly stopped tumbling with pins, but this might be an exception...

That said, this all looks like surface corrosion, so they'll probably shoot fine as-is.

 

[KingClown]

Looks like corrosion pitting to me. But its hard to tell from a picture.

 

[atblis]

If it was a suppressed firearm, the extra blowback gases can be corrosive to brass.

 

[Threeband]

Try a little gentle polish with steel wool.

 

[madmantrapper]

That looks nasty.

 

[Uncle Duke]

Try a little gentle polish with steel wool.

Yep. I'd try a bit of Flitz. If that won't clean it up, it's likely deep corrosion, maybe even complete with pitting.

 

[Harrys]

I bought over 100 6.5 CM cases from a guy without looking at them. Just a bunch of cases in a bag. They had been sitting in his garage for a couple of years after initially being fired out of an AR-10.

I tossed 'em in my vibratory tumbler and when they came out they were all nice and shiny except...90% of them had this rash on them to a greater or lesser degree. I tried scraping it off with my fingernail and washing it off and even tried a little steel wool. But to no avail.

Any idea what I'm looking at? Just plain old corrosion?

Any options other than tossing them in the garbage?
View attachment 448144

Brass corrosion is a natural electrochemical process when a brass alloy is exposed to air and moisture. Brass corrosion comes in several different forms and, depending on the corrosion mechanism, this corrosion can be either protective or destructive. In one case, brass can become oxidized due to atmospheric exposure to form a protective corrosion product known as patina. In another case, if the brass contains unfavorable quantities of zinc, a destructive corrosion process known as dezincification can occur. Tumble them and they should be OK. If you see pitting after cleaning toss them.

 

[atblis]

Suppressors - Suppressors cause immediate cartridge corrosion??

Was shopping bulk ammo on the Wilson Combat website when I saw their claim that suppressors will cause brass-cased ammo to corrode so quickly and severely that it will be difficult to extract the cartridge within 48 hours. I don't know how else to say it. . . I'm skeptical. Seems like if this...

www.snipershide.com

 

[4g64loser]

Just to bring this thread full circle, these are the cases pictured above but they have been cleaned properly. Some still.have a slight discoloration at the necks. There are a few damaged ones (these were definitely shot through a gasgun with a can) that will need to be culled and scrapped. The majority should serve just fine for any purpose other than match level precision. This picture was taken after a second round of wet tumbling, two hours each session. The first round mostly dislodged the absolute crap ton of walnut media that was attached to both inside and outside of cases. Significant carbon scale remained. Placed the cases in a bowl with alcohol warmed to about 100 degrees F for a while. Second round in the wet tumbler after soaking took the mess off.

Don't know if this information will help anyone but here it is. These cases will go back to boisepaw so he can use them.

 

[FN509Fan]

It's a miracle!

 

[4g64loser]

It's a miracle!

Hahaha. No miracle but they are at least usable now.

 

[boisepaw]

Awesome!

So I need to learn something new here.

When you say that there was a ton of walnut media on them…I‘m pretty sure I did that. Without really looking at them first I dumped them all in the vibratory tumbler and let it run a really long time.

Why would that have built up on the cases? I haven’t seen that before.

I did switch right after that to my Franklin rotary tumbler for a bunch of other cases…just water and some Lemi Shine…and was amazed at how clean they got. But running theses cases through the rotary tumbler (once) didn’t seem to clean them up.

 

[4g64loser]

Awesome!

So I need to learn something new here.

When you say that there was a ton of walnut media on them…I‘m pretty sure I did that. Without really looking at them first I dumped them all in the vibratory tumbler and let it run a really long time.

Why would that have built up on the cases? I haven’t seen that before.

I did switch right after that to my Franklin rotary tumbler for a bunch of other cases…just water and some Lemi Shine…and was amazed at how clean they got. But running theses cases through the rotary tumbler (once) didn’t seem to clean them up.

OK, I'm going to advance an *opinion* here so nobody take it as holy writ. I am not a chemist or materials engineer. Just a dumbass mechanic.

I went back and re read the OP. Apparently these cases sat in an environment with no climate control for an unknown period of time before OP got them. They were definitely shot through a gasgun, confirmed by OP statement. The gasgun was *probably* suppressed based on the amount of funk (not counting the walnut media) present. Based on anecdotal experience, I will say that the sooner you decap and clean cases shot this way the less likely you are to have issues. Another option based on my testing is to neutralize the residue but at that point why not just decap em and tumble em and just dry em once? Cases that have nasty residues (suppressor gas blowback) and are exposed to moisture soon or immediately after firing will exhibit permanent discoloration, as seen on some of the necks above even after two runs in a wet tumbler with alcohol soak between.

I use Dawn and lemishine in my wet tumbler. Pins too. For especially scuzzy stuff, i use an industrial floor cleaner that is available through janitorial supply houses and some chemical companies. I dont suggest that route for most people as it is borderline corrosive and you need to clean the material VERY thoroughly after tumbling or you can roach your entire load of brass. Tumbler and.pins must likewise be thoroughly flushed. I like the insides of the cases whistle clean and I accept the extra work to separate the pins after cleaning. Not everyone feels this way and that's OK. No pins works fine to get the outsides very clean, especially if you are looking to maximize the amount of brass you can run per load. Particularly with pistol cases.

TL/DR: decap and wet tumble your cases as soon as possible after firing, particles if you are as picky as me and/or you shoot a lot of suppressed semi or full auto.

 

[boisepaw]

OK, I'm going to advance an *opinion* here so nobody take it as holy writ. I am not a chemist or materials engineer. Just a dumbass mechanic.

I went back and re read the OP. Apparently these cases sat in an environment with no climate control for an unknown period of time before OP got them. They were definitely shot through a gasgun, confirmed by OP statement. The gasgun was *probably* suppressed based on the amount of funk (not counting the walnut media) present. Based on anecdotal experience, I will say that the sooner you decap and clean cases shot this way the less likely you are to have issues. Another option based on my testing is to neutralize the residue but at that point why not just decap em and tumble em and just dry em once? Cases that have nasty residues (suppressor gas blowback) and are exposed to moisture soon or immediately after firing will exhibit permanent discoloration, as seen on some of the necks above even after two runs in a wet tumbler with alcohol soak between.

I use Dawn and lemishine in my wet tumbler. Pins too. For especially scuzzy stuff, i use an industrial floor cleaner that is available through janitorial supply houses and some chemical companies. I dont suggest that route for most people as it is borderline corrosive and you need to clean the material VERY thoroughly after tumbling or you can roach your entire load of brass. Tumbler and.pins must likewise be thoroughly flushed. I like the insides of the cases whistle clean and I accept the extra work to separate the pins after cleaning. Not everyone feels this way and that's OK. No pins works fine to get the outsides very clean, especially if you are looking to maximize the amount of brass you can run per load. Particularly with pistol cases.

TL/DR: decap and wet tumble your cases as soon as possible after firing, particles if you are as picky as me and/or you shoot a lot of suppressed semi or full auto.

GREAT information. Thanks so much.

I love learning new things from folks with lots more experience than I have.