Current knowledge concerning the introduction of shipboard artillery in Europe is limited. A small, muzzle-loading cast copper-alloy gun recovered off Marstrand on the west coast of Sweden may, however, provide some important leads regarding this development. The cannon dates back to the 14th century CE and is believed to come from a shipwreck.
The Marstrand cannon. Image credit: Bo Niklasson / Bohusläns Museum.
In the summer of 2001, a small, archaic-looking cannon was found in open sea, approximately 5 km south-west of the island of Marstrand on the west coast of Sweden.
It was lying at the foot of the large shoal Hannehakarna, partially buried in sediment at a water depth of approximately 20 m.
The discoverer, a local scuba diver who at first did not understand what he had found, managed to bring the heavy piece to the surface.
Some time later, after having realized the importance of the find, he notified the Maritime Museum in Gothenburg about his discovery.
Archaeologists concluded that it was a shipboard cannon, and not a cannon that was being transported as cargo, because it still had parts of a charge left in its powder chamber when it was found.
This means the cannon was loaded and ready for use in combat at the time it ended up on the sea floor.
Thanks to the preserved remains of the charge, it has been possible to use radiocarbon dating to establish the age of the find.
“The lack of reliable typologies often makes isolated finds of early pieces of artillery difficult to date,” said University of Gothenburg maritime archaeologist Staffan von Arbin and colleagues.
“However, thanks to the cloth fragment, the Marstrand find offers a rare dating opportunity, as radiocarbon dating of the textile would indirectly also date the gun.”
“Fiber samples were for this reason extracted for radiocarbon analysis. The result came back as 635 years before present, which provides a likely date to 1285-1399 CE.”
“This could potentially date the gun as far back as the 13th century, although a 14th-century dating is much more realistic in view of existing written and pictorial evidence.”
The overall length of the Marstrand gun is 47.5 cm, of which the rear 27 cm constitute the powder chamber and the front 20.5 cm the barrel. It weighs, in its current conserved state 18.7 kg.
The barrel is of large caliber and slightly funnel-shaped, tapering towards the powder chamber which is of much smaller diameter.
The researchers documented the find with 3D scanning and conducted a chemical analysis of the metal used to cast the cannon.
The analysis showed that it was a copper alloy containing about 14% (weight) lead and only small amounts of tin.
This alloy is far from optimal for casting cannon according to the researchers, and it is likely that the cannon would have cracked and been rendered unusable if used intensively for longer periods.
“Clearly, the person who cast the cannon did not have the necessary knowledge and understanding of the properties of various copper alloys,” von Arbin said.
“This shows that the noble art of cannon casting had not yet been fully mastered at that time, and that production was largely based on trial and error.”
“The analysis also indicates that the copper ore used in the cannon’s production was mined in present-day Slovakia, while the lead probably came from England or the border region between Poland and the Czech Republic.”
Funnel-shaped cannons of the Marstrand cannon type are usually attributed to the 15th-16th centuries, but this find is testimony to the fact that this model already existed in the 14th century.
The preserved remains of the charge in the cannon’s powder chamber also show that the use of cartouches, a kind of textile packaging for the powder charge, came into use much earlier than previously known.
“Now, of course, we also want to try to locate and document the ship that the cannon belonged to,” von Arbin said.
“Although it is probably severely degraded and broken up, it should be possible to find scattered remains of the wreck if we conduct a thorough inventory of the site and its surroundings.”
The results were published in The Mariner’s Mirror.
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Staffan von Arbin et al. 2023. The Marstrand Cannon: The earliest evidence of shipboard artillery in Europe? The Mariner’s Mirror 109 (3): 260-282; doi: 10.1080/00253359.2023.2225311
