There is a simple way to decide what a dogs intentions are if you have a pistol.
Squat down and extend the pistol out as far as you can reach. The dog will try to bite the nearest thing to him. If he bites the pistol,pull the trigger and you don't have to worry about missing or where the bullet went.
If the dog stops before that, No Harm Done.
I agree with Master Blaster
Except if the dog leaps for your throat... Game over. You lose.
The reason dogs go for a trainers arm is because the man is standing, leaning over and extending his arm in such a way that the forearm is all that is available for the dog to bite.
I really don't believe that the dog will always go for what is nearest.
Sometimes dogs bite your leg, sometimes they leap up on you.
As an aside, my personal rule for dogs in my yard... Don't ask don't tell. People really love their dogs and will never speak to you again if you kill their dog. Mind you, I would only shoot an aggressive dog. I always try to make friends first. I have had a calf and one of the kids pet rabbits killed by neighbors dogs at different times. I finally decided enough is enough. Fortunately no agressive dogs have been in the yard since I made that decision But, if the neighbors would call and ask "Have you seen my dog?" and I was responsible for his demise,I would simply reply "Nope. haven't seen him"
I hope I don't burn for a lie like that.