Wrought iron bombards, early 15th century

Such short-comings help explain the gap of over a century between the introduction of firearms into European warfare c. 1330 and the beginning of the period of their real effectiveness c. 1450. The only way to ensure against fatal explosions was to forge extremely thick and heavy barrels, created not by casting iron (for which the technology was not yet available in Europe) but by hammering together red-hot iron bars and then wrapping them in further heavy iron rings. As the length as well as the girth of cannon increased, so did the problem of moving them from one place to another. ‘By the middle of the 15th century, the core of European artillery was represented by huge bombards of wrought iron which could only be moved with great difficulty, aimed very approximately, and reloaded very slowly.’ (Cipolla, Guns, Ships and Sails, p. 27).

A prime example is this medieval supergun from Styria (Austria), which, like many of its contemporaries, was given its own name: 'Pumhart von Steyr'.  Only 2.5 meters in length, this weapon has the largest caliber of any known wrought-iron bombard: some 76 cm at the base and 88 cm at the mouth. The iron rods of which the barrel was composed can be clearly seen in the mouth of the weapon, as can the iron bands which helped keep them in place. The thinner tail of the weapon held the powder charge. Weighing around 8000 kg, its charge of 15 kg of gunpowder could fire a stone ball 80 cm in diameter and weighing 690 kg to a distance of roughly 600 meters.

Further reading: Christian Ortner, 'Der "Pumhart von Steyr", Heeresgeschichtliches Museum, Vienna (15 Jan. 2018): includes detailed photos and illuminating technical drawings; Volker Schmidtchen, 'Riesengeschütze des 15. Jahrhunderts. Technische Höchstleistungen ihrer Zeit', Technikgeschichte, 44.2 (1977), 153–173, here 162–4.