This just isn't simple anymore and it gives me a headache. Back when bows were 50% to 60% letoff(a couple were 40%) and shooting fingers, at 65-67 lbs. I was shooting right around a 540 grain arrow.......2216's to be exact. I even dabbled a couple of seasons with 2219's at 70 lbs., till I figured out that 70 lbs. was just a tad too much for me when it got cold. When I started shooting a release. I still hunted with a heavy aluminum arrow. I blew through deer with no problem, but admittedly the arrow would not shoot as flat at longer distances.
KE was not even talked about then, at least not that I can remember. Certainly the correct arrow spine and weight most certainly was, along with FOC. I remember going to lighter arrows.....2213s for 3D shoots and eventually wound up using them for hunting. Next I used carbons, nearly the same weight but with a stiffer spine for hunting. And although I still killed my share of whitetail deer, I did notice a difference in penetration on not pinpoint hits and in fact even a passthrough on double lung hits were not quite as impressive.
I guess what I am getting at is this. Using the KE formulas, charts, etc. it doesn't work for me. I get better penetration, consistency and accuracy with heavier arrows shooting the same poundage, using the correct spine, and although the lighter arrows produce more fps( and in general according to the charts and KE formulas more KE..........well). It just doesn't work for me. For example I prefer an FOC of around 10%. Using a chart and more importantly to me is doing the balancing act at home on a level desk or table.......going heavier in broadhead weight along with the stiffer spine/heavier weight arrow does work for me. I am not talking about ultraheavy or over spined arrows. Simply using a heavier weight that is properly balanced within the accepted FOC range. Shooting lighter to get faster speeds and in effect to pump up the KE, well I just don't see it working.
What I am saying is, and remember this is my opinion....as unexpert as it is, I would not rely simply on formulas, graphs, and charts alone. I just think KE is way overblown and too many archers are basing their arrow choices on it. Thats my opinion and I am stickin to it.