Navy,the reason that foc affcts penetration is simply that when the front end is too light and the arrow encounters resistance,the back end of the arrow will try to pass up the front.This kick will take the energy that the arrow has and direct it in a different direction.


This is why someone with a higher ke level can get by with less foc than someone with low ke imo.Ke is actually the energy in the arrow that allows the arrow to remain parallel to it's original position throughout it's motion.An arrow that flies straighter or has the ability to fly straighter will penetrate better.