‘How to make a shot of lead and stone (the stone being put in the mould in which the leaden shot should afterwards be cast) to be of the like Diameter and weight as an iron shot is of. I Have found by experience, That if you take five parts lead, and one part stone, it will come very near the matter, wanting not much above three ounces [85 g], which is nothing respecting the difference you shall finde in Pibble-stones: Here I have framed a Table of how much lead, and how much stone must be together to make the equal weight of iron shot, from one inch [25.4 mm] to eight every half inch [12.7 mm].’¹²¹

While the use of stone could enable a lead round to be brought down in weight to that of a round of solid iron, this clearly cannot be achieved when the inclusion is itself is of iron. Yet Wright’s manuscript of 1563 states that a round shot intended for a falcon, with a calibre of 2 in (51 mm), would weigh 1 lb 12 oz (794 g) if made of iron, while it would weigh 2 lb 5 oz (1,049 g) if made with lead and iron dice.¹²² The important conclusion we can draw from Wright is that consistency in reduction of weight was probably the intention of the mid-sixteenth-century gunner, just as it was for Nye, but that the reduction was simply to another standard.

The desire for consistency is logical, for this would allow a gun captain to accurately judge, from experience, what gunpowder charge and gun elevation he needed in order to engage a target at a given distance. Indeed, if he used the correct stone inclusion in the round shot then he could use exactly the same charge and elevation for lead composite as he did for iron shot. If this was the normal practice with composite rounds then we can look to the objects themselves for the proof. This is not practicable with rounds from the Mary Rose and other wreck assemblages, because corrosion has both reduced the weight of the iron dice and has caused distortion of the lead sphere.

It is possible with the well preserved composite rounds now available from Bosworth (Figures 7.26). The graphs shows the diameter of each round in relation to its mass, comparing this to the relationship of mass to diameter for ideal spheres of lead, cast iron, wrought iron and limestone. For the lead-stone composites there is a fairly close correlation to solid iron rounds, as one would expect if Nye’s principles were being followed. For the iron dice there is far less consistency, although much of the variation could be a result of the inaccuracies in our initial measurements of diameter, for even the solid lead rounds do not all lay in exactly the correct position. It remains to be seen whether the correlations are strengthened or disappear when more accurate data is available from the 3D imaging. However, the initial results, taken together with the evidence from both Wright and Nye, suggest that the late fifteenth-century gunners were not saving lead in a haphazard fashion. Instead they seem to have been carefully manipulating the mass of the projectiles to ensure a consistent ballistic performance.

If reduction of mass had to be carefully controlled then why bother to make a composite round in the first place? If the principal objective was simply to save money by using less lead then why were iron dice used as an inclusion when stone was clearly just as effective. Indeed, given the extra costs involved in manufacturing iron dice, one wonders whether there was a significant saving at all.