my understanding is that buckshot was, back in the colonial days to probably civil war era, a 'big animal multipurpose shot' that could kill animals up to and including bucks, but was just as likely to be used on a wild hog, turkey, mountain lion, or whatever...and generally was shot at animals after you either treed them (mountain lion) or stalked up on them
then again, you have to remember the attitude was a bit different. I've heard an old timer (and of course NOT one from the flintlock era) who would talk about hunting deer with a 38-40, which when you asked about how effective it was "ya, sure, worked great, ya yust stalk close ya see, and ya shoot em two er tree times and he gooes right down like nottin'
lots of hunters in the 1920s or so had no qualms about stalking close to a herd of deer, popping up at 25-50 yards and blazing away at the herd as the herd ran until their gun was out of ammo or the deer were out of sight, and then you'd collect the two or three you downed, follow the bloodtrail from any you might wound and get them too. You'd come home from a hunting weekend sometimes with no deer, sometimes with 5.