MO,
I agree, the numbers sound crazy...that's why I don't like to use KE for much, if anything. The formula for momentum is weight x speed / 225218. According to your numbers, the heavier arrow is producing 0.5322 slug-feet and the lighter arrow is carrying 0.5065 slug-feet. This amounts to 5% less energry for the lighter arrow. When you combine this slightly lowermomentum of the lighter arrow with the fact that the heavier arrow will slow down less quickly over a given distance due to air friction, then the increase in momentum will be more like 8% for the heavier arrow over the lighter one. You are correct, however, that this is merely academic if deer is the largest game you will be hunting. But I'm hoping that I was able to make a complicated idea somewhat easy to follow so you can see why I choose the heavier arrow; that 8% gain may just be the amount that I need to get through a shoulder blade after apoorly placedshot. I practice every day to not need that extra, but I still consciously make the choice to take the best chance I have got to the woods. Good Luck!