Pointman - Do yourself a favor and stick with the military rounds!
If you reload, you should use 168 grain Sierra Match King HPBT, and IMR 4895 powder, in accordance with a good reloading manuals' high and low ranges. Preferably use 3 different manuals because 1 manual could have an error, and if one is different than the other 2, follow the other 2. The load suggested above is close to the load Federal Gold Medal Match Cartridges use, and it works very well. IMR 4895 was designed for the M1 Garand, and it works very well in the M-14/M1A as well as in the AR-15, as well as in . . ., being a very good all around powder for most cartridges, a good one to keep around.
As to the bullet weight, DO NOT EXCEED 180 GRAIN BULLETS FOR ANY REASON!!! The system was designed to be able to shoot bullets of 180 grains and below, if you exceed that bullet weight the Operating Rod Spring will bottom out and you could have failures of the Operating Rod and/or the rear of the receiver. I have seen them in the broken state (I have never seen one break, but I have seen them about a minute or two after they broke.), and the owners were not happy campers, wanting to sue the cartridge manufacturer, CMP, Springfield and anyone else who was close by. M1 Garands are getting more rare as time goes by, and you do not need to destroy one, besides the steel in them is between about 48 and 63 years old, and no need to overstress them. They will function for the next 500 years, as long as the owners respect them, and do not abuse them.
Do yourself a favor and stick with the military rounds, or reload your own as I have stated above!
If you choose to reload, there are at least three rules to live by (and I am sure there are others, who will suggest more):
1) WHILE RELOADING, DO NOT ALLOW YOURSELF TO BE INTERRUPTED, PERIOD!!
2) DO NOT HAVE MORE THAN ONE POWDER ON THE RELOADING BENCH AT A TIME!
3) DO NOT PUT POWDER BACK INTO ANY CONTAINER!! (It works well as a fertilizer, spread it sparingly over the lawn or in the flower beds.) It is far cheaper to dispose of 8 lbs of powder, than to destroy a rifle!
I have never had much luck with any en-bloc clips other than the 8 round M1 Garand clips. I do understand the state 5 round limit requirement must be met or you could have a problem with the "Game Warden", or whoever would check your rifle. Another problem may exist in some states, like here in California, you are not supposed to use FMJ bullets while hunting, be sure to check on the state law where you intend to hunt.
`