Broadhead weight!!!! FOC calculations, come on! I don' t think a calculation is the way to go. Go out and buy different weights, and just shoot them. What do you shoot best with. I was shotting 100 grain for while because I wanted more speed. Fact is I was' nt shooting very consistant. I started messing around with arrows and different grain weights. I found I shoot mcuh better with a 125 grain broadhead. My groups are much more consistent, I get better penatration, and I still get in the 290' s. It takes a little time, but lets face it, the best way to get an idea of what to shoot is to actually go out and shoot. No calculations can take into account the intagibles of shooting. Everyone shoots different and every bow is different. Shoot wth what you shoot best