In the military(police) one of my duties in Africa/SEA and US was animal control on runways. 00 buck from a cylinder bored 12ga is close range work, bird shot (Note the term BIRD) is useless. I had one feral dog run away dragging his guts shot with a 110gr Sierra HP .30-06 @ 3100 fps in an AB dump that we never found! Never use Heavy-Shot(Gov't too cheap-thats a joke now), but #4 buck 3" and #1 buck 12ga worked very well under40 yds. When I was able to use my guns back in the CONUS-Mossberg 535 w/ full choke added 10 yds to the buckshot loads and 223 from M16s/Rem700 HB Varmint rifle and Savage M10 .220 Swift put it out to almost as far as you can safely see on an AB! As of my retirement 200+ dogs/cats/varmints. That count includes 21.5 yrs as a State Police officer where dogs were dispatched on search warrants, rabid/sick animals found on patrol and feral dogs seen hunting/working. Several coyotes exposing themselves during day time, crossing country roads, etc, met their fate with a Ruger MKII HB pistol/Red dot sight loaded with CCI Velocitors. Feral cats too. 1 bobcat acting sick midday passed via .45ACP.