Whereas the full octagaon smoothbore appears to have been common, note that they were tapered and flared ("swamped")like the rifle barels. These were typically built like rifles, with rifle architecture and rear sights. Some of these may have started out life as rifles and bored out or worn smooth later; others may have started out as smoothies. It is amazing how many of the "rifles" pictured in the noted books like RCA v1&2 and Kindig, etc, are smoothbored. :m2c: