One thing is, forget Kenetic energy calculations. Your main concern is penetration and "Hit Poundage" is much better factor to determine penetration. The heavier the arrow the less speed you need. I've always believed that for hunting big game (deer bear etc...) you shouldn't hunt with less than 40 "Hit Pounds" of energy. You would only need to push a 600 gr. arrow around 145 fps to obtain that and that's plenty for complete penetration on deer or black bear.