Those are all very good points todd1700 and probably an accurate assessment of why expandable heads dont penetrate for most, however the fact remains that if people would properly tune their bows they really wouldnt need mechanical heads in the 1st place. Penetration aside, I think the problem remains of mechanical heads opening prematurely, or worse, not all. whenever you have moving parts, those parts can move or fail to move when needed. those little tiny screw that hold the blades on dont inspire much confidence in me either. if someone has confidences in expandables, i say use em and love em, but I personally dont see any advantage over fixed heads, and i dont think you need poke giant holes in deer to spill alot of blood on the ground.