Tony mutters from a corner...
"Some of those no-face things seemed tougher than others. Some I could clock on the back of the head hard enough to put them on the ground with one shot. With others, that same shot didn't do a damned thing besides get them riled up. Of course, there was zero way to tell before until it connected, so you roll the dice and get out of the way if you hit a ringer.
I saw a couple take two pistol shots and keep on swinging. Not sure if any took three, or how they held up to rifle fire.
Oh, and they also really didn't like people going for cheap shots. Just drove them berserk.