Back in my early days I worked in a packing house where we killed about 1,000 head of cattle a day. For the most part they were all killed by cutting the major arteries in the neck with a knife after they were stunned with a pneumatic knocker and hanging upside down from a rail. The really tough ones that came back alive from being knocked had to be killed before they could hurt someone and they did that with a .22 pistol shot to the head. Granted that was point blank range, but those were 900 pound adrenaline filled cows or bulls with lots thicker bone structure than any deer. I'm not sure what bullet they used and that was 40 years ago. Bullets are way better today than they were back in the '70's. That said, I killed a car hit deer that had a broken back to end it's suffering using a .22 pistol and it was less than decisive.
