FWIW, I shot a nutso Neighborhood Dog that had been chased from my yard with a paintball gun many times. This time he had a hold of my wife's 3 pound Maltese. It was a Mutt with some Rott in him, probably about 60 lbs. I hit it with a .40 from about 5 feet and it dropped instantly. It was an original Black Talon bullet, they were still fresh enough to have in a carry gun at the time.
(Of course, I waited until any respectable dog would've been able to have shaken the life outta that little rat of dog that my wife had....
) It survived, but sadly (yeah right) it was crushed by a large SUV tire a year later.