there is a Hahnbüchsflinte on egun that will probably ending cheap if anyone is looking for such a 19.century beast. described as 16/65 shotgun barrel and 14x60R rifle barrel I would say the rifled barrel is chambered for the 28 ga lancaster bullet cartridge with 40mm long brass case. blackpowder only in this damascus barrels of course.

http://www.egun.de/market/item.php?id=3494609