M2 would be correct, according to TM 43-3001-27 "Army Ammunition Data Sheets Small Caliber Ammunition" the M2 ball was loaded with 50 gr. 4895. They show pressure right at 50,000, but many things have changed since then, powders and especially the accuracy of pressure testing. I believe current data puts that load a little hot, we use 48 gr. 4895 with Sierra 150 bullets and they work beautifully. I only use this at ranges that use the 100 yard course (reduced targets of course), when I shoot the other ranges, (200 to 600 yards) I use 47gr, 4895 with 168 HPBT bullets. I've used Hornady and Sierra HPBT match and can see no difference. By the way, this is the NRA approved (max) load for the M1 Garand, (46.5 gives about the same results). A note, this load through my 1903A3 shoots groups smaller than a dime, the rifle has absolutely no modifications.
I would recommend getting a copy of the manual, I got mine while in the service and do not know if there is one available electronically.