Comerical '06 ammo can be used in the garand. The problem is with the bullet weight, heavier bullets hammering the op rod. You keep the loads to 15-180 range you are good to go.
Many years ago, I was a Light Weapons Sgt in a Reserve (NG) Special Forces company. I was taske with putting on a clinic for shooting the A4 Machine Gun, BAR and Garand. We didnt have time to go through the system to obtain 30 Cal ammo but was able to come up with the funds to purchase comerical bullets. We fried the com. ammo in all three guns with out any problems. Later in my Career, as OIC of the AK NG Marksmanship unit, I ran sniper schools using the M1C&Ds, plus, providing qualification for the AK State Malitia (differant from the NG) and Navy Reserve, using the garands. Again no ill effects. When small arms came under the guidence of the Ord Dept, & Springfield Armory, the normal process before a rifle was issued was to fire a test load @ 70,000 PSI, for each gun. Defects for the most part were weeded out.
As for reloads, I rairly shoot anything but 168s and 180 (now the 175) SMKs, using 47 grns of 4895, which closely matches the 30 cal US M72 match.
Keep your loads or com. ammo down to 150-180 grn bullets @ aprox 2700 fps and you'll have no problems with your Garand. I've been shooting my CMP (then DCM) Garand I got in the early 80s since then, with both comerical, Reloads, and M72 Match since then. Only thing I did to it was bed the stock and put on NM Sights.
In Gen Hatcher's HATCHERS NOTEBOOK there is a section on the 'Strength of Military Actions". I recommend you read it, you'd be supprised of the strengt of the actions. One must take into account there is a differance in the methods used in determining the pressures and it leads to confusion.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071