Lynn,
I don't know what you're reloading for, but if I were you, I would start around 43-46 grains and see how it goes from there. Lot safer to do that with your M1 Garand rifle and not risk damage the op rod if you're a bit too hot.
The 1:10 twist of most 30-06 barrels doesn't do that well with 150 grain bullets, especially after 300 yards. So loading it hotter isn't gaining you a whole lot. You'd be better off buying something around 175 grains for the 600 yard line. Better accuracy, as that's fits the twist much better.
Regards,
Dave