Come late to this thread, was searching something else.
I've told this story before, shot two rabbits in quick succession with the HMR, both head shots, first one disappeared, second one did the most impressive death dance I've ever seen, when I went to pick it up found the first one, it had rolled over with no subsequent movement, I struggled to find any sign of wound, after careful looking I saw a tiny drop of blood in it's temple, the bullet had passed straight throu its temples leaving hardly a sign. The second rabbit which had done the dance was totally different, the most damage I've ever seen from a HMR, the entire 'face' of the rabbit was gone leaving just the lower jaw and back of scull virtually no brain left, so movement after being shot is no indication of life.