I haven't seen or even heard of any in decades, but there were some smoothbore .22 "rifles" and pistols made for firing shot capsules (they could fire ordinary

I haven't seen or even heard of any in decades, but there were some smoothbore .22 "rifles" and pistols made for firing shot capsules (they could fire ordinary bullets too). The ones I know of were intended for "snake medicine" where rattlesnakes were common. The reason for the smooth bore is that firing shot capsules out of rifled barrels leads to "blown patterns", that is areas where there are no pellets, especially towards the center of the pattern which is where you are actually aiming the gun.