My hunting buddy was shooting Montecs and he loved them at 20 and 30 yards, then went back to 50 and that was when the whistling became really noticeable and they would not group as well as field points. (Still pretty good though)He was turned off by the noise, so he bought I believe Wasp's Boss Bullets to tryand his groups tightened up at longer ranges and no whistling. This kid's bow is as tuned as one can get. The only thing I can think of is he is shooting 305 fps so maybe they can't take that kind of speed.