Boy if this is not the age old argument,,Nothing has been found to out penetrate the Rocket Steelhead and I do mean nothing...This test has been done several times in the past(with ballistic gellatin,plywood,steel drums,and dead cow hindquarters) Miles Keller did one of the most recent tests....Of course they may need to be double banded depending on the speed you are shooting, I have found that the expandables that do not use bands have a chance of opening when the speed reaches over 400fps or are exposed to a massive amount of energy from high poundage bows(crossbows in particlular)...One of the few fixed broadheads that seem to fly at high speeds are the WaspSST 75 or 80g heads.Also their Jackhammer(I prefer Rockets bands over Wasp bands) does a number on whitetails...I have tested the WaspSST 75g at speeds exceding 450fps and hit to point of aim...