Excellent info people.
Custerman, it was my sons first time shooting the M1. I have actually been shooting for quite a while. All milsurps, so I learned about corrosive ammo early on.
My rule of thumb is trat all ammo as if it is corrosive. Part of the fun for me is cleaning it up when I get home from the range.
One thing that I do that has proved wuite effective in inhibiting rust and keeping the bore shiny is giving the warm barrel a squirt or two of Windex with ammonia, and letting it run down the bore. I dry the outside off and clean it up good with Hoppes No 9 when I get home. The ammonia neutralises the corrosive elements of the rounds.
All of my rifles' bores look better than the day I bought them, due to my diligence.
I got to pondering my original question, as I said, after shooting the other day. I was thinking about grandpa, and the fact that his unit was on the move at a rapid pace during the last months of the war. I guess they took every opportunity to grab a bite to eat, and keep the equipment functioning properly.