Arrow weight can vary a fair amount before you notice any real difference in point of impact. However, the amount of weight difference that you are talking about, leads me to believe that you are using different size arrows. Or arrows that are cut to very different length. If this is the case, you will see a difference that is not satisfactory for hunting. Remember, in hunting situations, you have factors that are hard to control, such as adreniline, weather conditions, and movement of game. When you add up all the possible problems that are out of your control, you really need to use equipment that will shoot as good as possible.