The so called Berne gun, preserved at the Historic Museum Berne, Switzerland; sadly not seen on display for decades like almost all their weapons.
The oak stock is the original one while the hook nailed thru the stock seems to be a working addition of ca. 1430-40 when the first hooks turned up.
The stats are:
oa. length 95.2 cm, oa. weight 4.15 kg, barrel length 18.5 cm, octagonal throughout, length of bore 15.0 cm, outer muzzle diameter 5.6 cm, bore 3.5 cm.
A very similar wrought iron barrel, ca. 1380-1400, and retaining one of its originally two iron stock bands, is in my collection (attchaments below). Its eight sides alternate in width which, according to my experience, is characteristic of almost all of the earliest octagonal barrels. Like on the Berne gun, the touch hole is some 3 cm forward of the rear end. Unlike the Berne gun, the bore of my item has been drilled out within its working life. You can see the drill marks on the inner wall of the barrel, as well the place on the bottom which the point of the drill left. This accounts for its present cylindrical bore which most probably was of conical shape originally.