" The benifits of speed : 2 K.E.relative to heavier (slower) arrow "
Actually, no. Simple physics dictates that a heavier arrow will absorb more of the bow' s energy. The end result is a slightly higher Ke with a heavier arrow. The Ke difference is minimal, but by increasing your arrow mass your momentum greatly increases.
Ever wonder why in order to hunt dangerous game in Africa, by law, you have to use a heavy arrow (something like 900 grains)? It ain' t because " speed kills" .
" I have 82# K.E. with a 62# BK2 useing a 315gr. arrow @ 342f.p.s."
Cool. Call a PH in Mozambique and tell him you want to hunt Cape Buffalo with that set-up. Don' t take his laughing personally.
Speed and Ke figures are good for one thing though...they sure do sell a lot of new bows every year.
JRW