In its most basic form the technology of the early modern gun is not highly complex. It consists essentially of a tough, fracture resistant tube, or ‘barrel’, closed at one end, into which is inserted gunpowder. A wad may be pushed into the barrel to hold it in place, before a projectile is put in. This may itself be confined by further wadding. A very small aperture, otherwise known as the ‘touch hole’, or ‘vent’, near to the closed end of the barrel, provides access to the charge. By inserting a pricker into the vent the gunner clears the hole of any obstruction or residue and pierces the cartridge, and then ‘primes’ the hole with a little more powder. By applying fire to the hole – by means of a hot wire, or piece of smouldering match cord, for example – the piece is discharged. ‘Black powder’ which was the gunpowder of the period – a mixture of saltpetre, sulphur and charcoal – combusts very rapidly. The charcoal acts as a fuel, and the sulphur helps to produce a stable reaction, but without the presence of the saltpetre to provide plenty of oxygen the burning would achieve nothing. As the carbon from the charcoal combines rapidly with oxygen forming large quantities of carbon dioxide and energy, so pressure within the gun barrel increases very quickly, driving the projectile out of the tube at great velocity.

Gunpowder made significant advances between its first use on the European battlefield, about 1300, and the early Stuart age. What had once been a rough confection of approximately equal parts produced by methods best described as mid way between alchemy and cookery, had gradually been refined and improved in a number of ways. Perhaps most importantly the proportion of saltpetre in the mixture had gradually been increased until in 1635 powder for English government service was fixed at a ratio of six parts to one each of sulphur and charcoal. This is not so different to the formula accepted as optimum by the lights of modern science. Another significant advance was the introduction of ‘corning’, or sieving the powder, whilst damp, into granules of given sizes. This apparently simple process not only provided air gaps between the grains which aided rapid combustion and gave greater power, but made the powder safer due to easier handling and reduced dust, and also reduced separation and damp problems.