Given that all but one round recovered from Bosworth has a calibre below 65 mm, it is likely that most of the composite guns fired in the battle were gutter-built, but not all the guns will have been of composite construction. Two types of solid barrel were also in use in the later fifteenth century, one forged from wrought iron and the other cast from bronze or iron, all of which had a smooth bore. What is not known is how common these types were in the 1480s. There are only a small number of cast bronze guns remaining in collections of early artillery, compared to composite wrought iron barrels. However, as cast bronze barrels were particularly easy to melt down for re-use, the surviving collections may grossly under-represent the numbers of cast guns in use in the late fifteenth century.

The earliest solid type in common use, for all but the smallest of artillery, was probably the forged barrel of wrought iron. It would appear, from failures seen in several such barrels, that they were constructed by wrapping iron around a former and hammer welding this to create a single piece barrel.153 Visual examination of the barrels constructed in this way reveals a high degree of irregularity in external form (Figure 7.44). However, it is the interior of the bore which determines the signature left on a lead ball. It is clear from all such barrels that we have examined that the bore has a far more consistent geometry than is seen in composite barrels. What it has not yet been possible to establish, is whether the manufacturing process has resulted in sufficient irregularities, compared to cast barrels, to leave a distinctive firing signature on a lead ball. This will require highly accurate 3D recording of the whole length of the bore of a number of examples of both types of barrel, rather than basic measurements at the muzzle and internal inspection with a borescope so far undertaken.

The final type is the barrel manufactured by casting around a former, which is likely to be the latest type to have come into large scale use because of the difficulties in achieving consistently strong castings (Figure 7.45). The only exception may be barrels of the very smallest bore, which were already being cast in brass for battlefield use by 1461 because, as we have seen, fragments from two such barrels have been recovered from Towton.

As with round shot, so with gun barrels, the casting process enables a high level of uniformity in manufacture both of individual barrels and between different guns. The consistency of the internal geometry, compared to composite barrels, is immediately obvious from visual inspection, although some minor irregularities can be highlighted using strong, low angle lighting (Figure 7.46). Experimental firing, using a highly consistent modern steel tube, shows that a lead ball fired from a barrel with a regular smooth barrel produces a firing band with a consistent curve, although sometimes deeper sections of banding may be produced. Where round shot has a similar consistently curving band then this probably indicates firing from a solid barrel (Figure 7.35).

These barrels could be cast from either bronze or iron. Because cast iron guns were heavier, they were better suited for garrison use, where they were fired from fixed positions, or for naval use where the gun platform itself – the ship – moved into position to deliver fire. For a field army, where mobility was a major consideration while on the march, during deployment and then manoeuvring with the infantry, the bronze gun was the ideal because it was lighter. While the vast majority of artillery pieces in later centuries were muzzle loading cast guns, in this early period some cast guns were also manufactured as breech loaders. In both Murten and Vienna there is a cast bronze example of a breech loading barrel which mimics the external form of a composite gun. This may indicate that they were manufactured at an early stage in the transition from wrought iron to cast bronze field artillery (Figure 7.45).