This is good info, but really only a portion of it pertains to paintball, the majority is for precision semi-automatic weapons, sniper rifles and automatic weapons, and as for your question there SgtScot, the 2/3 rule really does not apply to paintball at all, as the trajectory of the round can change dramatically based on many factors like moisture (in the barrel and the atmosphere, as in rain or snow) gas pressure/velocity, composition of the paintball, etc, etc.