Brass corrosion

[Jowens]

What causes this? Should cases be tossed?

Brass is brand new, but maybe old stock Lapua.

 

[918v]

Chemicals in the cardboard that react with moisture in the air and attack brass.

 

[jhazelwood]

Green corrosion is bad, not sure that the black stuff is more than tarnish
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[pell1203]

A couple of days ago I was at the range and a fellow a few stations over was shooting a 300WM he'd gotten passed down from his dad and tried shooting a leftover box of original (about 40 year old) ammo. First few rounds, he said, seemed to go ok. Next one blew some material on his face and the recoil was violent enough to bang the scope against his eye, draw blood, and jam the bolt to where it could not be opened by applying significant hand pressure. Overall, the ammo showed some tarnish and an overall brown discoloring, or fine dusty residue, on the outside of the cartridges (significantly worse than what you show in your picture). After the incident, closer inspection of the previously fired and ejected cartridges showed one with a split neck. However, even more alarming, several of the remaining unfired cartridges also had noticeably visible cracks on the necks. Overall, he was a lucky guy... hope his rifle is also okay!

Jowens, you are probably okay to shoot what you have as your ammo is in much better visible shape than this guy's. However, please stay safe and look each round over carefully before shooting to confirm that there is no unexpected stuff going on. Stay safe!

 

[Jowens]

These are the only two out of 100 that have it. I'll probably throw them out to be on the safe side. The other 98 look new like they should.

 

[Greg Langelius *]

When in doubt, throw it out.

Brass may be expensive but costs are relative.

Hate to have a permanent reminder that I couldn't afford to part with a piece of brass that is valued in cents, or even a few dollars.

Greg

 

[Greg Langelius *]

Some insight into the material can be found here.

There may be a factor called 'season cracking' at work here, where atmospheric ammonia attacks the zinc in brass, causing something that could be at the root of the neck cracking mentioned above.

Greg

 

[Deadshot2]

From time to time I've encountered cases that have spots like this. I use Stainless Steel pin media in my tumbler and I just run them through with a batch. This takes off all the surface discoloration and the actual "corrosion". When the cases come out of the cleaning process I sometimes can't find the cases that had these spots. If they remain and there is any pitting I just toss them out. So far I'm 50-50 on the "save" versus "toss".