I find it hard to believe that a mechanical will not open.With that said,I've killed at least 15 deer with mechanicals over the years and never lost a single deer.I killed one deer with the original 2 bladed spitfire.I had a dead deer and no damage to the head.I killed two deer with rocket sidewinders.I bent some blades but none broke.I killed three bucks with steelheads and broke one blade on two of the deer and two blades on the third.I recovered that deer but it was one of the toughest tracking jobs.The deer ran a half circle for about200 yards in some thick steep terrain.I've killed a bunch of deer with Wasp jackhameers also.While I never acually broke a blade,the ferrule broke more than 50% of the time where the black of the blade makes contactand the blades were just hanging there by a wire.

It depends on what you consider failure.I guess I never experienced a failure because I never lost a deer.However,the inconsistant results I got with mechanicals caused me to go back to fixed blades and I've never looked back.