I have experienced the same with trapped coon but only when I was shooting at an angle toward the bone..their skulls seem to be very thick and rounded for their size and I would get poor penetration even with dead center bullet placement. I have never experianced this with any coyote, free or in a trap although granted I have shot many more coon. I think it is easier to get a flat angle impact on their larger heads....but once again, your bullet placement is head only, distances allowed have to be much more limiting and you definately want to at least be using hypervelocity solids...trust me coyotes can run a long way when even shot with something like a stinger square in the chest. There are easier ways of doing the job.