Using the "doppler chrono" that attaches to your bow, I have different readings. All arrows, tips, etc are the same using the same bow and poundage etc. The difference between arrows is anywhere from 315-294. It seems the higher end is the same arrow with most othersreading 294-300. My question is, one how accurate are these chronos and is this a normal difference in readings. 21 fps to me is a big difference between them all. Or would I be lieing if I said my bow was shooting 315fps? thanks for all.....Mitch