I picked up a bunch of 1X 30-06 brass from a buddy who had fired it in his M1919. It is all from some crates of Chinese ammo he had. He was planning on reloading it, but at a casual glance at the batch of unprocessed brass sitting in a box on his bench, I noticed one had the tell-tale shiny line indicative of the incipient head separation. I used it as the opportunity to instruct him on the case inspection and what to look for. He was surprised with the fact of the case and a couple of others in the batch with the impending failure.
So, long story, he decided to give me the entire batch. It's all boxer primed and I've already ran them through the annealer. I know I will need to watch closely and will be checking with the paper clip method after each sizing.
Some of my 308 and 223 brass was MG fired as well. Those came from Uncle Sam and were fired in M240's, M249s and M4s.