I and some friends used everything from birdshot to 00 Buck on a pack of feral dogs, and #4 Buck was included in the mix. Naturally, the birdshot was only immediately lethal to the dogs at about 10 yards or less We were sitting on top of a hunting shack (old trailer), and they had been harassing us. We went up on the roof with our shotguns after setting some bait (mostly garbage with a pound of hambuger in it) and waited. About 10 PM, they came in, about 20 of them, everything from terriers to Labs. The bigger stuff, 00, 1 Buck, 4 Buck, T, F, BBB, etc., down to about #4 shot dispatched the dogs well with head or chest hits out as far as we could see them. (Only two of the 5 of us were good shots on moving targets) The birdshot would make them yelp and back off for a bit, but they'd start back in. We whittled them down to about 5 dogs before they scattered and ran. I still remember shooting a beautiful black Lab, wish I didn't have to, but they were not afraid of people.