I've killed several with a smoothbore, all with a single shot, but it wasn't a single shot shotgun. I've used Remington 870s and Ithaca 37s. all 12 ga. I've used both slugs and buck, both have been effective. This includes my biggest buck, a 4.5 year old 9 point on Fort Custer. If you have to use a smoothbore, and want to use slugs, I recommend the Federal tru-ball loads, they've been very accurate for me. And reasonably priced.
