I have three Garands (two Springfields and a Win-13), and I have used a lot of different powders in all of them. I also use cast bullets as well as jacketed bullets in all three. I generally like to use the slower burning powders whether I am using cast or jacketed bullets. All three Garands shoot and function well, and I have never had to replace any op rod or other parts on them. Well, that is not quite true. On my one Springfield, the original barrel was opened somewhat at the muzzle, and it did not shoot as well as the others. After a lot of consideration, I finally replaced the original barrel with a new one, and it now shoots better than the other two. I could not bring myself to sell the original barrel, but it really does not make any sense to keep it. They are all great guns.
One further thing I might mention, is that I do not shoot hot loads in my Garands. I have used a lot of different powders, but I have started with low loadings and worked up to where the action functions reliably and the accuracy is best with whatever bullet I am using. My cast bullet is a Lyman Loverin gas check design that weighs about 152 grains. I generally use 150 to 165 grain FMJ-BT for jacketed bullets. In recent years, I have opted for the IMI Mil Spec bullets that are available at good prices.