Jeff, it is NOT reasonable to assume an arrow reacts the same way when it hits flesh as it does when it hits an inanimate object, like a target.... unless it hits solid bone, like the ball and socket in the shoulder, and immediately slams to a dead stop.

On a broadside hit where the arrow knicks a couple of ribs, it's not going to have much resistance. An arrow going a mere 200 fps when it hits a deer is going to whip through the deer in about .008 of a second, assuming a 20" wide ribcage. Doesn't give that arrow much time to flex, does it. By the time the arrow could react to the impact, it's already through the deer and gone.

Talk about small diameter and friction. What's the difference in friction between a carbon arrow with stiff plastic vanes and a 2419 wearing feathers? The carbon shaft is smaller and, naturally, has less friction, but those vanes! The 2419 has more surface area and more friction on the shaft, but those feathers slide right through. Prove it to yourself. Grab the shaft of a vane fletched arrow and pull the fletching through your closed fist. Then do the same with a feather fletched arrow.

I agree about momentum/KE being over-argued. Like I said, you don't have one without the other. Like YOU said, with a high performance bow you can stack up a pile of KE and do well. On the other hand, while you're stacking up that KE with speed, you're also stacking up the momentum. That's why a high KE arrow will penetrate. Not so much because of the energy but because it's also carrying a lot of momentum. Don't take my word for it. Do the math!

It's easier and quicker to pile on the momentum with arrow weight than it is to get it with speed, but you do get it with speed. Still, momentum is the key, as far as I'm concerned.

Where I get my dander up is when KE snobs start saying you must have X amount of KE in order to ethically hunt such and such animals. Not only are they operating with a false premise, their BS is dangerous to youth, women, disabled and traditional hunters, who cannot shoot high poundage bows or whose bows cannot churn out gobs of KE. Momentum is a much better indicator and is easily achievable for most people.

Lets assume for a moment that my suggested minimum of .33 pound seconds of momentum is a good figure. I don't know that it is, but lets assume... That is achieveable with a 500 gn arrow at 149 fps and 25 ft lbs KE. - ie. a 50 pound selfbow. Or a 400 gn arrow at 186 fps, 31 ft lbs - ie. a 12 year old with his youth compound. I don't like the idea of using less than a 400 gn arrow for hunting so I won't figure for a lighter arrow.

Those low KE setups will do the job BUT, you have to have make intelligent choices in arrow selection, broadhead selection and shot selection. You have to have the bow well tuned. You have to execute the shot properly and place the arrow accurately.

Of course, those same choice and performance issues are imperative no matter whether you're shooting a wimpy rig or a mongo rig. It's easy for the hunter to blame the arrow for his failure, even though it's hunter's fault because he chose the wrong arrow to begin with.