I got my case of Guatemalan 5.56 in today. The brass all looks good, a few spots on a few cases – that's all. But the copper is a different story. Most of it is pretty tarnished. A lot of the bullets are almost black. It cleans up with Tarn-X ok, but I was wondering if there's any reason not to use it. I believe it will shoot just fine as is. My goal was to get a can (840 rnds) of ammo on stripper clips and in bandoliers out of this case for "contingencies" and just shoot the rest. 180 rounds were near perfect. I'd like to clean up another 660 rounds for storage. Any reason not to use the Tarn-X?

BTW my battle-paks are all camo colored, marked 08 Mar 1989, Lot 1

Thanks
Scott

From what I understand, Tarn-X, Brasso and the like contain amounts of ammonia and ammonia is bad for ammo.  Weaks the brass supposedly.