Don't own an M1, but still hope to never stress this brass because I don't load max anything.....at least not on purpose. I have had a couple of rifles, for whatever reason, showed pressure signs before other same chambered rifles or the loading tables said there would be any.
I ended up with a large amount of once fired std and match military brass in an estate I helped a family with. The old fellow shot at Perry and would collect fired brass, deprime and tumble it, and stack it very orderly in 50 cal ammo cans. I sold may of these cans on the net and kept one of each variant for myself. I think the 61 FA, a coupe of different years of LC (both match), and one can of unfired, primed, but empty of TW(?), and some fired but dirty LC issue stuff. I can't imagine any better brass being available and have enjoyed using it.
You fellows cannot imagine all of the cool, unique, diverse, and just plain interesting stuff I pulled out of that old gent's basement. I would have loved to have known and been around him while he was alive! As it was, I had the distinct feeling that he was looking over my shoulder while I was down there. I got three pickup loads plus one utility trailer full of stuff including some really neat firearms. I know it was dumb, because his family certainly had no use for or interest in the stuff, but I handled, and sold, his stuff with as much reverence as I could. I ended up buying a couple of the guns I could afford and made the widow a fair price on all the odds and ends of things that would just be pretty much unsellable. I still get a satisfied feeling every time I make use of those things.
Here is how I found the brass. Unfortunately, I couldn't find a pic of a full can, but imagine brass stacked like this to the top and other stacked sideways in the middle gap also. All the case mouths would be faced inward and not disorganized as in this partially full can. There was literally no way another single piece could be packed in.