I agree, need more info. You exact Kinetic energy figure is best, but if you have your bow make and model, draw weight and draw length along with your arrow syle I can make a pretty good " guess" . I agree with the others however the spitfires are fine mechanical heads, but they do open slower than most, and with the 1 1/2" cut they won' t penetrate as well as a smaller head. I would personaly prefer a fixed blade head for elk, but I have tested a few mechanicals that will work pretty well if you have the right setup and a well tuned bow.