Art, you Do realize that in your water test your gonna need a VERY long tank. Arrows being very aerodynamic (And hydrodynamic) will go though water much better than a bullet that turns into a mushroom in impact.

Get that sports car up to the same KE as the freight train....and you ain' t gonna stop either on of them!!!

experianced dangerous game hunters don' t go for slow and heavy...they go for heavy and whatever speed you can put behind them..and hit accurately.
Can someone tell me how fast is TOO fast to kill game?

Once we get to that nice 600gn arrow at 400 fps...much of this won' t matter....if it does at all even today!

A SHARP head put in the right area can/WILL kill deer dead...very cleanly. Within reason, it doesn' t really matter how heavy or fast it' s going. Arrow bounces off of a shoulder blade? don' t hit the shoulder blade!!! That' s a tough challenge for ANY set up...no matter how fast or slow! A buddy of mine who ALWAYS shot heavy/slow (recurve with Zwickey heads) told me the SAME story about HIS arrow bouncing off....and how he WISHED he had his Mathews THAT day!!! (He just won it...doesn' t shoot the recurve much any more....personal choice)

Shoot what you will...if it works for you...GREAT!!! I' m just saying that there is MORE to penetration than momentum.