Sorry, 'Nando,
I must admit that I overlooked that but it makes sense.
In this case, that beast is even younger, late 1st half 16th c., closely comparable to those found on the wreck of the Mary Rose, which sunk in Spithead harbor in 1545, and to another large specimen, 46 cm long, bore 40 mm, weighing 54 kg and formerly in my collection.
http://www.vikingsword.com/vb/showth...breech+loading
Best,
Michl