… the Alderney guns were new, or virtually new at the time of their loss. Very likely they reflect the earliest English pattern for cast-iron muzzle-loaders, a type of gun that would remain in service for over three hundred years and which, at Trafalgar in 1805, would put an end to Napoleon’s dreams of European conquest. Technically speaking, they would not be surpassed until the Armstrong rifled, breechloader of 1859.
In broad terms, the Mary Rose guns of 1545, looked to the past; the much smaller collection from the Alderney wreck of 1592 were totally different and looked to the future. Only 47 years separate the two vessels, but in that period nothing less than a revolution had taken place in gun design, manufacturing and ballistic science.
For most of Elizabeth’s rule (1558 -1603) England was in a state of war, or under threat of war. In 1588 it had to fight off a major sea-borne assault; but the spectre of invasion hung over the country long after the destruction of the Armada. Foreign policy mattered more than ever before, which implies, for an island nation, a major role for the navy, and for that navy to be effective it had to convey credible threat and, when necessary, win battles. Guns, therefore, were more important and more in demand than ever before, but to understand fully their technological and historical significance, one needs first to know a little concerning their design and operation.
Guns are tubes with one end open that function by the ignition of a compound in the closed end, or chamber, that results in a massive expansion of gas. The resulting forces are channelled along the tube, or barrel, propelling with them any unrestricted object towards a specified target. The combustion of the propellant is explosive, that is to say the released kinetic energy radiates out with equal strength in all directions. The barrel has to be designed with enough strength to withstand the pressure of the explosion and concentrate it in such a way that it will drive the projectile in the desired direction. If the gun cannot withstand the blast, it will either (depending upon the metal) become distorted or explode. At best this results in the ruin of the weapon, at worst in the annihilation of the gun crew. With the improvement of propellants (to which we will return) and the greater pressures they created, gun barrels evolved from tubes into something more cone-like with their body walls thickest at the breech where the shockload was greatest. As the forces move down the chase they become significantly less allowing the metal wall to diminish in thickness; but reinforcement was still needed, particularly at the muzzle where, upon the expulsion of the shot, the pressure drops from about one-third of maximum pressure to zero in an instant. On early guns the muzzle was reinforced with a series of rings, but, with the higher muzzle velocities resulting from the improved propellants, these were replaced by a swelling. It is believed that the swelling first appeared in naval artillery about twenty years before the Alderney guns which show the feature in its still emergent state.
To understand the gun, one needs also to understand a little concerning its carriage. A common lament of gun specialists is that virtually no reliable diagrammatic documentation on gun carriages exists before 1722. In broad terms, however, it can be said that the early tube-guns were often bedded into flat-bottomed stocks, or sledges, of a kind that were found on the Mary Rose; then, at some stage, the guns were given trunnions, or cylindrical side-projections, which not only served to fasten the gun to its mount but also functioned as small axels upon which the barrel could be elevated for greater range. The positioning of the trunnions was important as that effected what was called the ‘preponderance’ of the gun and its ‘jump’ on discharge. If the preponderance was not right it could prejudice both the accuracy and efficacy of the piece. Usually the trunnions were positioned just a little forward of the barrel’s centre of equilibrium; but if they were too far forward, the breech would be over-heavy (or have too much preponderance); on the other hand, if the trunnions were too far back, the muzzle would dip on firing. In terms of their fore-and-aft placement, the trunnions on the recovered Alderney gun seemed to be about right, but, typical of early guns, they are low on the barrel; in time they would be sited closer to the centre-line.
With the introduction of trunnions the old bedding system no longer had a purpose, instead the gun became supported by blocks which were connected by a transom and given wheels for motion. For sake of stability the carriage was kept low and sited as far back as possible so that the muzzle and some of the chase could protrude through a port thus projecting the heat and flames of discharge as far from the hull as possible, for on wooden ships the greatest fear was not storm, but fire.
Apart from the report and its muzzle emissions, the most obvious response of a gun on firing is recoil. ‘To every action there is an equal and opposite reaction’ (Newton’s third law) and as the projectile moves forward, the gun moves back. Obviously, a gun of many hundredweight cannot be allowed to move about freely as this would inflict damage on hull and crew, destabilize the vessel and, in an artillery duel, create chaos on the gundeck which would slow down the rate of fire. The gun had to be controlled and the recoil limited, and this was done not through the gun but through the carriage. Firstly, the trucks (crude wooden wheels) on the carriage were small, for not only did this help reduce height but also the smaller the trucks the less their efficiency and the more resistant they became to rotation. Secondly, there was the breeching, that is to say the roping of the carriage to the vessel in such a way that it dampened and broke the recoil, and then, after loading, allowed the gun to be run out for refiring.
In addition to the old stock-type guns mentioned above, the Mary Rose also contained our first examples of trucked naval gun carriages. Each example, however, was different. Clearly the carriage was still in a developmental or transitional phase, and no fully-evolved, standardized pattern at that time existed. Particularly interesting is how the sides of those Mary Rose carriages known to the writer are in two parts; the forward supporting blocks with their recessed grooves at top to seat the trunnions, and, behind them, separate timbers that were stepped to provide a series of fulcra for levering the gun to an appropriate angle of elevation. ‘At some point’, speculates Caruana, ‘the two parts, the stepped plank and the trunnion support, were combined into a single cheek’, thus almost completing the development of the carriage into the conventional form that would not change significantly until after the Nelsonian era. Only a part of the carriage survived on the single gun that has so far been raised from the Alderney wreck (Monaghan and Bound, 2001, fig. 21, 50), but it is enough to show that the trunnion block and stepped component have merged into a single timber. If, as we think, all the cannon on the seabed are the same, then it is likely that the carriages will also be of identical type, thus demonstrating that by the time of the Alderney ship there was a fully (or almost fully) evolved, standardized pattern for naval gun carriages, and that, therefore, the Alderney guns represent the end of a period that was one of transition as much for carriages as for the barrels they supported.
So far we have managed to avoid the subject of gunpowder, but probably the most central influence on gun and carriage design was the propellant, the ignition of which created the violence necessary to impart motion to the shot. Between the Mary Rose of 1545 and the Alderney ship of 1592 a new type of powder was introduced that had far-reaching consequences and which, together with the developments that have just been discussed, and others to which we will turn, mark the forty-seven years between these two vessels, as not just a period of transition, but one of revolution.