KE doesn't seem to change significantly when changing arrow weight, on the same bow. As weight increases, speed decreases. Momentum determines penetration. Of course, KE is a factor here, also. But a heavier object resists opposing forces better than a lighter one, if speed is roughly the same. There comes a point where one overrides the other. At what speed and arrow weight this occurs can probably only be borne out by testing different setups. One interesting thing I came across when testing arrows was a lighter (not much, 15 gr), stiffer arrow worked better with my bow, regarding penetration. This was found shooting broadheads into a foam target. Both arrows were spined OK for my bow. Redline 410 at 29" and PSE 300 at 29", both with 100 gr heads. The PSE is on the stiff side, by the chart, but shoots and penetrates much better.
Trushot, you definitely need a new bow.<img src=icon_smile_big.gif border=0 align=middle>
Phil.
"Could you guys be quiet, my dad's trying to shoot."<img src=icon_smile_shock.gif border=0 align=middle>