The reason for the wide variance of IBO speed is because Diamond advertised 310-318, shooting a 350-grain arrow using a 70# bow with a 29” draw. I duplicated their efforts and the best I averaged from 12 shots was 290. I used 2 different types of chronos producing the same results on all shots. The Black Ice I reviewed had the timberline package which include a couple of accessories which might have effected the IBO Speed.