I should mention that in the aforementioned French museum of Castelnaud there are three more early wrought-iron barrels, two of them of relatively large and heavy dimensions, mid-15th c., and comparable to two heavy pieces in my collection:
Please note that the term 'petards' assigned by the museum is not correct; petards were actually installed to blast fortified places, e.g. their gates.
I will once more post photos of my related pieces, mid-15th c. and ca. 1480 respectively.
The third however, quite small, obviously octagonal and with alternatingly wide flats, the breech seemingly struck with a mark, seems quite close in period to our barrrels of ca. 1400 discussed here.