[DreadMagus]

To be honest, I doubt the military would be that efficient.

For the main reason they're dangerous - their training... Aren't most soldiers trained to go for the center mass instead of the head on normal targets?

Now apply that to enemies who will not go down due to torso shots..... by the time people actually realize the only way to kill a zombie is with a headshot/blow - and... well... there might not be much military left.