Coyotes are hard to kill. I have no luck calling them but do kill afew running them with dogs and setting and waiting on them when running corn, so all of my coyotes are running, of at least 90% are. I use 55 gr. Varmint Night Mares in my AR. These are thin skinned varmint bullets and usually stay in. The problem is that with thin skinned bullets if you hit one running from you penatration is not deep enough to get to the vitals. I stick with them because they knock the coyotes down and I can get another 2 or 3 shots off while they are getting up, and I don`t what to have to worry about long rickochets. The thin skinned bullets are ok for side shots into the chest, but from other angles they are lacking. Personally I don`t worry about the size of the hole, as long they I get them killed. At $ 5 ea., which is what they are around here they hardly pay for the gas to the fur buyer anyway.