What you're experiencing could be a number of things. First, what's your draw weight and length, arrow length, broadhead weight? It's possible you're borderline on shaft stiftness and the broadhead characteristics put you over the line. Also, depending on what you're shooting into and how much you shoot, carbon arrows will loose their spine over time. When I shot Bemans everything in the charts told me 400's should do it. They shot just fine with fieldpoints. When I went to broadheads they were totally unexceptable. I switched to the 340's and the problems went away. I could have more than likely cured the problem with a lighter broadhead, but since I already owned about 2 dozen Thunderhead 125s I jut got new arrows. Of course the problem could also be your tune isn't correct, but they still should group somewhereeven if it wasn't exact.