The numbers they give you are minimums as far as arrow weight goes. I like heavy arrows myself. Mine are a bit over 500 grains, maybe 550 I'm not sure. As long as your arrows are at least as heavy as they recomend you should be fine. You end up with a little more energy with heavy slow arrows than light fast ones but the light ones shoot alot flatter. Dont matter to me as I limit my shots to 30 yards & to be honest havent shot at a deer over 25.