Cast iron Tudor firearms
The wreck of Henry VIII’s warship the Mary Rose, which sank off Portsmouth in 1545, included a previously unknown type of firearm – listed in contemporary inventories as hailshot pieces. These small guns are about 40 cm long and are still loaded with a cluster of small chunks of iron that give them their name. Unlike other surviving guns of the period these were made of cast iron. How were they produced and were they effective?
The gun is now entirely penetrated by corrosion, but the surviving microstructure indicates a composition of white cast iron. After casting, the liquid metal solidified in a very distinctive way, with elongated crystals extending from the outer surface of the gun towards the inner. This indicates that the external mould had a much higher thermal conductivity and was almost certainly made of metal, whilst the core would have been of sand or clay.
Although we do not know this gun’s place of manufacture, its date coincides with the first claim for successful iron gun casting in England. Potentially, cast iron was a highly attractive material for gun casting: traditional wrought iron firearms required much time to forge to shape and the long-established casting alloy, bronze, was much more expensive. The use of a metal mould could have enabled very rapid production of these guns. However, this study showed that the product had an extremely brittle structure, totally unsuitable for containing an explosive charge. The findings explain a rapid decline in the deployment of these weapons, as recorded in the ships’ inventories. In 1546 there were 459 hailshot pieces aboard 58 vessels; by 1547 only 82 remained.
The results of this investigation a full publication of the finds from the Mary Rose wreck, and have already been published in the Royal Armouries Yearbook. The findings, as befits discoveries of international importance, have already begun to be widely disseminated.