"These instruments which discharge balls of metal with most tremendous noise and flashes of fire...were a few years ago very rare and were viewed with greatest astonishment and admiration, but now they are become as common and familiar as any other kinds of arms." (Francesco Petrarch, c. 1350)
Born of an emerging technology and military expansion of Middle Eastern and Asian empires the cannon quickly became the mainstay of European armies as well. At first more a psychological weapon than a killing machine, through continued use and innovation cannon came to the forefront of increasingly larger and more mobile armies. Soon artillery came to be called the "mistress of the battlefield."
Bronze vs. Iron
Early cannon were often forged. They were made up of bars of iron welded together and reinforced by iron hoops shrunk around the outside (there are even instances of hardened leather cannon made in this way) But casting soon became the preferred and easiest method.
Bronze was initially used for guns because of its relative ease of casting compared to iron. Melting iron requires a higher temperature, thus more fuel, and the iron casting process is much more sensitive to oxygen, chemical impurities and the balance of alloying ingredients than bronze. Cast iron guns were available in the early 16th century but they were expensive and the failure rate was high.
As the casting process was perfected iron cannon became more numerous; iron guns were generally lighter and cheaper but offered the same amount of strength. Iron did have a drawback however, it crystallized overtime and became more brittle, thus iron pieces wore out quicker and could not be melted down and recast like bronze. At the end of their life-span iron guns were simply abandoned.
Bronze and other copper alloys continued in use from the 16th through 19th centuries, especially for presentation guns, some types of smaller guns and those intended for high-accuracy applications.These bronze cannon had a longer life-span, between 1700 to 2000 shots compared to perhaps 1200 for iron. Many survive because they never reached their useful limit.
Most fortresses and ships carried a combination of iron and bronze pieces. Choice of cannon was generally a matter of budget and the natural and technical resources available to a particular country. Bronze gun metal is over 90% copper, with 4-7% tin added. Copper was more readily available in Europe, with the primary source in the 17th century the mines at Falun in Sweden, which produced over 3000 tons annually in the 1620s, representing over 60% of the entire world's production. Most of this was exported to Europe.
Metal supply was one factor in the adoption of iron and bronze, but another was skill. The art of casting bronze or iron was not common, and many countries had to import guns or the craftsmen to make them. The Low Countries were an early center of gunfounding, and several countries including Spain established their own foundries around immigrant Flemish or Dutch masters.
Smooth-bore, muzzle loading cannon fired a variety of projectiles, from simple to quite specialized.
Round Shot: A solid projectile made, in early times, from dressed stone but, by the 17th century, from cast iron. The most accurate projectile that could be fired by a smooth-bore cannon, used to batter the wooden hulls of opposing ships, forts, or fixed emplacements, and as a long-range anti-personnel weapon. The effect of a careening cannonball bouncing across a field filled with columns of marching men would have been akin to a deadly game of nine pins.
Chain Shot/Bar Shot: A projectile used to slash through the rigging and sails of an enemy ship so that it could no longer maneuvre. Chain shot was two round shot linked by a length of chain. Bar shot was typically two halves of a cannon ball with a solid bar welded between. Called "angels" (possibly because of the fluttering noise they made as they rotated through the air) these were frightening weapons but relatively inaccurate and only used at close range.
Spider Shot: was a variation on chain shot, but it had many chains attached to the multiple balls instead of a single chain between two. It was not used very much, despite its effectiveness against small ships and morale.
Grapeshot: An anti-personnel weapon, similar to canister shot, but with iron shot being stacked around a wooden core and wrapped in a canvas bag, and generally of a larger calibre. So called because of the resemblance of the clustered shot in the bag to a cluster of grapes on the vine. In 19th century variations of this, the shot was held together by a coiled bar, essentially a spring attached to two end plates and was spread by a fused charge in the same way as a shell or the shot was sandwiched in layers between iron plates held by a central bolt. Effective range out to 900 yards.
Canister: A short range anti-personnel projectile made up of small iron round shot or lead musket balls in a tinned metal can, which broke up when fired, scattering the shot throughout the enemy personnel within range, like a large shotgun. It had an effective range from about 250 to 400 yards.
Star Shot or Faggot Shot: A cylindrical wooden shot, either a solid log scored into triangular bars or wooden rods tightly bound by iron bands. When fired they would split and splinter apart creating an effective and inexpensive short range anti-personnel munition.
Case Shot: An iron anti-personnel projectile containing an interior cavity packed with lead or iron round balls around a small bursting charge of just enough force to break open the thin-walled iron projectile. A hollow wooden fuse inserted into a hole in the outer edge of the projectile was designed to be ignited by flame from the propellant charge. Ideally the case shot fuse would detonate the central bursting charge when the projectile was six to ten feet above the heads of the enemy showering them with the iron balls and fragments of the case. Invented in1784 by Lt. Henry Shrapnel, of British Royal Artillery modern shells of this type still bear his name.
Shell: A 19th century explosive anti-material and counter-battery projectile, of iron with a cavity packed with a high explosive bursting charge of powder used to destroy enemy wagons, breastworks, or opposing artillery. Two types of fuses were used--impact fuses that detonated the bursting charge by percussion, and time fuses cut to length measured in seconds and ignited by flame from the propellant charge.
Carcass: An incendiary/antipersonnel projectile designed to burn fiercely and produce poisonous fumes. It was constructed of an iron frame bound with sack cloth and filled with various ingredients such as pitch, antimony, sulphur, saltpeter, tallow and venetian turpentine. It was ignited by the cannon's propellant charge, bursting on impact with the target and releasing noxious fumes while setting fire to its surroundings. It was effectively an early chemical weapon as well as an incendiary projectile.
Hot Shot or Heated Shot: A process where a solid iron cannonball is heated red hot in a specially-designed furnace and then is loaded in a muzzle-loading cannon, cushioned by a substantial thickness of wet wadding such as sod, and is then fired while still red hot, at flammable targets with the intention of setting them on fire. This was a much advocated tactic (and many times a very successful one) for shore based forts defending against attacks by wooden warships. Examples of these small brick furnaces may still be seen at permanently constructed pre-1860 forts in Europe and the United States. The adoption by most navies of iron hulled ships generally made these obsolete. The shot was carried on a specially-designed iron barrow or 2-man litter and, in the era of blackpowder cannon charges contained in cloth bags, occasioned much fanfare and notice as it was conveyed to the cannon muzzle as the red-hot projectile would easily ignite any carelessly handled loose powder. Any reckless or somewhat dangerous individual who seemed to draw trouble to themselves and those around them was referred to as a "Hot Shot", giving rise to the term in common use to this day.