The only time that I have ever seen two bows that were 15 fps different and shot nearly identically, was at a shoot when the guys were comparing their Hill style bows. In these comparisons, they were not quite identical at times, because some of the slower ones had more hand shock than the faster ones. Actually, I saw more than 15 fps differences that day with near identical poundages, arrow weights and draw lengths. I also saw how two people shooting the same bow and arrows with nearly identical draw lengths could get a 15 fps difference from each other. Then someone took out a Schulz all bamboo and let a few of us, that he trusted to not over draw it, try it out. Some bows were slower, some bows were faster, but that bow was the winner by a wide margin. It may be to much to ask at times, to expect two bows to have all things identical and have a wide spread in chrono readings.