I agree with Doe Killer on your bow needing to be tuned. There is another consideration though "ARROW SPINE"!!!!! If your arrows are not spined correctly to the bow your broadheads will never fly properly. When a broadhead is added to an arrow it will generally lengthen the arrow, which weakens the arrows spine. If your arrow spine is marginal to begin with you might have problems in getting broadheads to group well. There are solutions to the problem like lowering the bows poundage, decreasing tip weight, or shortening the arrow if possible. It is also possible to be overspined, but generally a compound will shoot an arrow on the stiff side very well. Its all a system that has to be worked out to get your arrows flying well. One of the advantages of a compound is that you have the option tune the bow to the arrow. Don't get stuck on a particular poundage. In hunting accuracy and shot placement will always outweigh speed. Three or four blades makes no difference, but the four blade models have more cutting surface in the same or similiar broadhead diameter.