I hunt pigs and sometimes goat with my shotgun. It's a smooth bore tho. I have come to the conclusion that buckshot is only good out to 20 yards but that you shouldn't use it unles you have to because of heavy cover where you will almost certainly hit some branches. The bad thing about it is that you might be tempted to risk longer shots out to thirty yards. I tried to hit some goats one time that were 25 or 30 yards out and even with the long barrel, the first shot while aimed at the head of one with the head and body of the other a couple feet to the side. First shot BOOM! Not a single thing even flinched. Not even did it miss the head, it completely missed both animals bodys. Next shot BOOM! The one I was aiming for dropped and the other ran off. Turned out that out of nine buck shot, only one hit the goat. Barrelly hit just behind the head only half an inch down from the top. Only stunned the animal. I got there and finnished it off. Out of 18 bullets, one hit where I was aiming. All others missed.

I tend to load a slug first and have buck shot for follow up shots but if the animals are far off, then having buck shot is useless and unethical.

I too have heard that in rifled barrel, they can mess up the rifling and do not group well.

And with buck shot, you have to realize that there is a very real danger of hitting the antlers, tusks, or horns. I've heard stories of tusks being shattered by buckshot. I think I'm gonna change my pig gun from a shotgun to a 44 mag semi-auto rifle just for that reason.