I have seen a section of barrel from one of Saddam's "Super-guns" at a museum here in the U.K.. The barrels were of a smooth bore and manufactured in relatively short sections and with a drilled flange at each end in order to attach to the adjoining section. If memory serves me correctly the section of barrel which I looked at was at the Imperial War Museum's Duxford site. This was some years ago and so I do not know if this exhibit is still there.