Jerry, I have done plenty of varmit hunting with a flintlock longrifle. Mostly ground varmits were a rifle seems to give more range. I have often thought it would be neat to have a shot load as well for the occasional crow, turkey or canada I might spook. And always in the back of my mind has been the chance of coming across a rattler or copperhead. Nothing better than those rascals to recognize the effects of a lot of lead.
I solved my problem with a swivel breech. One barrel rifled the other smooth and both in 50 cal. That has since changed to 54 cal as my son is using the gun for deer and canada's at the same time.
Just an idea you might consider. The extra weight also handles the recoil issue well.
Good luck with the coyotes, HIB