
I had been using both fixed blade and mechanicals for several years, trying to find the "perfect" broadhead. I had pretty well decided on the Wasp JakHammer 1¾" cut mechanical as being it. I had shot several (didn't keep exact count) deer with the JakHammer and even a poor shot (liver) resulted in a quick kill.
The deer in the pic was a case of mistaken identity by me. I thought it was a doe, but it turned out to be a button buck. It came in to my feeder in the quickly fading light of evening (in a north/south valley and when the sun dips behind the western treeline it's still well before the legal time to quit, but it gets dark quickly). I had my son with me in the ground blind 18 yards away and I was mentally debating whether to take the shot when my son whispered, "Those backstraps sure would be tasty dad."

Next morning I went back to the kill site in good light to look for my arrow. I found it quickly and when I picked it up I was shocked to find the blades on the broadhead still banded closed! No wonder the hole through the heart looked small! Even with the blades closed it still punched about a ¾" hole through the heart, enough to quickly drop the deer, but certainly not a shot I'd recommend or try on purpose!
I examined the broadhead careful and could find no apparent reason for the malfunction. The blades were free to pivot when I slid the band back and the shot had not been at a really extreme angle. All I could come up with as a theory is that it possibly missed hitting hard ribs and the tender hide and muscles of a young deer just weren't enough resistance to open the blades.
Whatever the cause of the failure I don't want to repeat it, so I switched to my favorite fixed blade broadhead for the rest of the season (G-5 Montec). The next season a buddy had some new Wac'Em Exit 4 blade broadheads he wanted to trade me for some arrows and Montecs. I took the trade and managed to shoot 2 deer with the Exits last season. Both of those were good hits through both lungs, and both deer were easily recovered as they only went a short distance.
My conclusion from all this simply is to repeat what all the "experts" have always said. Use a very sharp broadhead, put it where it should go (through the heart/lung area), and you will have plenty of venison to eat!
I will admit the mechanical probably was the reason the one bad shot (too far back and hit the liver - actually cut it in two) was an easy recovery, but for now I'll stick with fixed blades and just be very selective about shot placement and the angle of the deer at the time of the shot.