The issue with powder and Garand loads is the burning rate of the powder. If the powder burns to slow, you can have a still burning powder granule enter the op rod port and the increased pressure can bend the op rod. As stated previously, 4895 is the classic powder for it, and is what the military used to load Garand ammunition. 4064 also works well. You can use any powder with the same burning rate, although I would be hesitant to experiment. Keep the bullet weight at 168 gns or lighter. Have fun with it.