Actually it may not. I have seen many animals shot in the head or had the head chopped off that continue to move and function just fine for a little while. The best example would be cutting a chickens head off and it still can run around or fly for a while. I have shot many a farm animal in the head growing up and not all of them dropped on the spot.

Chances are if it doesn't drop though it certainly won't go far. That is providing you actually put that tiny bullet in the small hard to reach well encased brain of a deer. What if you miss by a slight amount and end up wounding the deer like blinding it or shooting it's jaw off?

In my opinion head shots on deer are about the worst shot you could take. Better left to poachers and other people that have little regard for the game they hunt.

My opinion anyway.

Paul