I like the Rocket Sledgehammer,any large dia. head will work.Some use a washer or adder behind the head. The idea is to expend all of the arrows energy in/on the bird,you don't want pass thrus,helps in putting him down quicker. I aim for a spot between the top of drumstick and wing butt from the side or center mass of body from front or rear,rear being preferred. I think the one you saw may be the guiotine?? made for head shots only,blades are thin but looks like it would wind plane to me. Be forewarned,YES it is worth it,you may not want to take the gun again.