I've always used 48 grains of IMR 4895 for both my garand and 03A3, with 150's and 165's. I know it's not the hottest load, but it sure shoots well in both rifles. I think the 48 grain pretty much replicates the military load. as for 50 grains, I don't know that a 1-2 grain difference will be a problem. maybe shoot a few of them them in a bolt rifle and check the cases, primers, etc., extraction, for any signs of excessive pressure.
IMR's website show loads up to 53 grains for a 150 gr bullet, but that's probably for a bolt rifle. Of course there's a gas port issue. the M1 is a pretty stout rifle. I would be a little more concerned if you were shooting in a rem 7400 or something.
NRA Life Member since 1990
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