That string must be PERFECTLY drawn in order to get good flight, similar to us compound guys drawing a bow from different nockpoints, we will get different Points of Impact (POI). I have a crossbow that I marked the string with a SHARPIE, precisely where the center is to ensure that it is drawn perfectly centered to result in better arrow/bolt flight. If it's a crossbow, you'd be better off with a 125gr tip, you're not going to lose much velocity, and you'll have better FOC. Try MARKING the string, and making sure that you draw it very consistently, and you should see better flight, and groupings!!! Good Luck.