I would not recomment mechanical broadheads for bear hunting. Bears and large trophy bears in particular are stocky animals with tough hides. I spend a great deal of time at my uncle's outfitting camp and have seen several bears lost when hit with mechanical broadheads. A good lung shot with a relatively fast bow shooting a tough fixed blade broadhead like a Muzzy will often bring a bear down within 20 or 30 yards. IMO fixed broadheads are better for bear hunting.