The M1 Garand is much like the Springfield M1-A in that it is best to use powders with a mid range burn rate. Stay away from slow burning powders and heavy bullets, or you'll wind up with a bent op rod. I have the new 8th Edition Hornady Reloading Manual, and they list a section of the .30-06 specifically for the M1 Garand. For 150 to 155 grain bullets it shows 42.3 up to 46.2 grains of Varget for loads in the M1 Garand. For 168 grain bullets it shows 40.3 up to 47.0 grains of Varget. Varget is a good mid range powder to use because it is not temperature sensitive, and burns relatively clean. I tried to scan the page, but it won't lay flat enough. If you need more let me know.
I bought 3 cases of the Greek HXP M-2 Ball ammo, (1,440 rounds), a few years back from the CMP. I got all 3 cases delivered Fed Ex for $381.00 at the time. I couldn't buy the brass that cheap. Anyway the stuff gives a hard bolt lift in my Browning A-Bolt Medallion in .30-06. I heard some guys were bending op rods with it in M1 Garands. The stuff is loaded hot! I would reload. That way you have better control, and can start out low and work your way up until you get reliable cycling. It's more of a PITA, but it's better than risking any damage to your new rifle by taking a chance with 45 year old Mil-Surp ammo. My Greek .30-06 ammunition was 1967 vintage. Bill T.