This is is straight from NRA M1 Rifle guide:

The warnings (reader asked a question re M1 reloading concerns) you have been given are good ones. Though it is a rugged, piece of equipment, the m1 Rifle has an "Achilles heel); its long, slender operating rod.    Operating rods can be bent to the point uselessness if continually subjected to propelland gas pressures that are too high.  Such too-high pressures are usually the result of either too-heavy bullets or too-slow burning powder, or both.  In military service, over the several decades that the m1 was either our primary or an important secondary arm, this potential fragility of the operating rod was not a problem.  Ammunition for the rifle was developed and loaded that did not cause overly high pressure to be exerted against the operating rod, and so did not damage it.  Handloaders, however, can choose combinations of components that will casue damage.   For best results, use powders faster than IMR 4320, and bullets of 180 grains weight, or lighter.  Suggested loading data for .30-'06 ammunition in M1 Rifles follows:

147/150 grain bullets -- either FMJ or HPBT
IMR 3031    48.0 grains
IMR 4895    49.0 grains
IMR 4064    50.0 grains
Win 748 Ball    48.0 grains
Acc AA2460    49.0 grains
Acc AA2520    51.0 grains
Acc 2495BR    50.5 grains
Hod H4895    49.0 grains
Hod BL-C2    49.0 grains
Hod H335    49.0 grains
Herc RE12    48.0 grains

165/168 grain bullets -- either SP, HP, or FMJ
IMR 4895    47.0 grains
IMR 4064    48.0 grains
Acc AA2520   47.5 grains
Acc 2495BR    47.0 grains
Hod H4895    47.5 grains
Hod BL-C2    49.0 grains
Hod H335    47.0 grains
Herc RE12    44.5 grains

173/175 grain bullets -- M72 or M118
IMR 4895    46.0 grains
IMR 4064    47.0 grains
Acc  AA2460    46.0 grains
Acc  2495BR    46.0 grains
Hod H4895    47.0 grains
Hod BL-C2    48.0 grains

180 grain bullets -- either SP, HP, or FMJ
IMR 4895    43.0 grains
Acc AA2460    46.5 grains
Acc  2495BR    45.5 grains
Hod H4895    44.0 grains
Hod BL-C2    47.5 grains
Herc RE12    41.5 grains

The charges listed are meant to approximate the performance of military ammunition using commercial reloading components, including cases.   In no circumstance should any charge weight be increased.   If military surplus cases are used, charges should be reduced by 1.5 grains to start.   Loads using tubular-grained powders such as IMR propellants do well if primed with conventional large rifle primers (Federal, CCI, or Remington).  Loads using powders such as BL-C2, AA2460  or AA2520 and Winchester "Ball" are best primed with Winchester's WLR primer or possibly a "magnum" primer from another component manufacturer.

Please use this info from NRA as a guide to reloading for your Garand rifle.

ST762