my brass turned black--why

[emmie]

went to load some 308GI MATCH LC brass. when i opened the ammo can this brass has been
stored in i find that it has black stains on a lot of it. this brass has been in storage of over 20+ years,and was new pull down unfired GI brass. not worried
about the primers,going to reprime, but the strength of the brass.
have tryed cleaning in tumbler,which removers some black,but not all.
do i have a problem with this???

thank you for your time
emmie

 

[mlheppl]

I'm not a metalurgist, but I believe that the reason your brass turned black is a due to two components. Oxygen and time. Brass is not a pure element, I believe that it has copper in it's chemical makeup. Just as a penny turns darker over time, so will your brass. I believe that the brass should be fine for reloading. However it is possible that the malleability characteristics of the brass has changed somewhat. Run the brass through the size press then inspect it for stretching and cracks. If it looks good then load up a few rounds and try it. The elements that turned the outside of your brass also worked on the inside of the brass. The wear on the inside of the brass concerns me more than the outside as this is harder to see and evaluate. This goes for all brass that I reload. Here is the method that I use to evaluate wall thickness on my brass. I take a stiff wire of some type. I bend the end 1/4" at about a 45 deg. angle. Slip the bent end of the wire into the neck of the case. Run the end of the wire up and down the entire length of the case. If there is erosion or pitting, you should be able to feel it with the tip of the wire. This one of the steps I use in determining how many times I will reload an individual case before discarding it. With your blackened brass I suspect that you may not get as many reloads out of them, but should still be good for several times.

Hope this helps, and if I'm wrong will someone please correct me.

 

[Grump]

Mine turns pretty black if I lose it on the firing line and find it the next spring. Very hard to tumble that stuff off. It's just an oxide and does not affect strength because of the microscopic layer of metal involved.

Get pits in it, though, and I would toss it. It gets 31 cents a pound for scrap in these parts.

 

[uglymofo]

I had some LC brass that was stored outdoors in a cardboard box for 3 years, unsheltered from the weather. It had a lot of black tarnish on it.

I soaked them in a 60 second bath in white vinegar (60 seconds works as well as overnight; I tried) and dried them for 20 minutes in a 200 degree oven. After a 2-hour session tumbling in corn cob media with 2-3 ounces of liquid car wax I had laying around, and they looked like they was going to church. In my opinion, almost any auto paint conditioner should work. I've used extra fine rubbing compound, oxidation cleaners, liquid waxes, they all seem to have enough of a cutting agent to clean brass. Mechanix Orange works real well as a cleaning additive, though the cases don't shine afterwards. The only thing I couldn't clean on the majority of the cases is the discoloration around the neck of my Hirtenberger. It looks like they've been annealed, and that won't clean.