Warmatrix

During the first half of the 14th century CE, the bombard evolved out of the earlier gunpowder weapon, the handgonne. While hand-held handgonnes improved mainly in rate of fire and reliability, bombards were artillery guns that focused on firepower.
The very first guns were "pots-de-fer", "vasili" and "sclopi", vase-shaped constructions that were ignited at the rear. These guns fired both stone balls and heavy darts. They were inaccurate, slow, unreliable and mostly employed to frighten troops who were unused to them.
Quickly, the vase shape evolved into an almost straight cilinder. As ammunition was not standardized and seldom fit a gun barrel precisely, bombards tapered slightly towards the rear, so that any ball of approximately right caliber would fit somewhere in the barrel. This design had the disadvantage that when the ball left the barrel, some force of the explosion would blast alongside it, rather than behind it, reducing firepower. The answer was to compensate by making guns as large as possible.
Thus the 'bombard' developed, though confusingly the name was also used for catapults that did not use gunpowder. Despite bombards being siege weapons, the early models were not very powerful, on par with older siege engines or even weaker. Their main advantage was their low cost. The barrels of these early bombards were made of wood, reinforced with iron hoops. Later they were constructed of wrapping an iron sheet or by spiraling a band. These weak barrels could leak or burst when the gun was fired.
Between 1420 CE and 1450 CE bombards rapidly evolved. By then, they were made of parallel iron staves, reinforced with iron hoops. This allowed for longer barrels, which increased rate of fire, firepower and accuracy and lowered the cost. At the same time gunpowder quality was also improved, when gunners switched from "serpentine" a.k.a. 'mealed' powder to crumbled and corned powder. This deteriorated slower, was less vulnerable to moisture, ignited quicker and more evenly and so packed 2 - 3 times more power. It was so powerful that the gunsmiths had to use less effective sub-optimal powder, to prevent the explosions from rupturing their guns.
These new powerful guns could quickly batter Medieval city and castle walls to rubble. They helped the shift of power from local barons ruling their provinces almost as independent states to kings ruling larger kingdoms. Some of the heaviest bombards, like those used by the Ottoman Turks at the Siege of Constantinople, were up to 8 meters long, weighed 19 tons and could fire a 275 kilogram stone a mile away, though only seven times per day. This prompted defensive walls to be redesigned in the middle of the 15th century CE, leading to the development of star forts. A variant of the bombard was the mortar, a short-barreled gun that shot its projectiles at a high angle. This survives to this day as a light infantry weapon, the trench mortar.
Bombards were big and cumbersome. The earliest ones had no carriage; they were simply laid down on a pallet. While the largest could fire over vast ranges, smaller ones had to be dragged quite close to the enemy walls. This was a difficult business because of counterfire by the besieged. Smaller guns were also developed, called "culverins", which could be carried into battle by one or two men. These were used not only in sieges, but also on the battlefield.
After improvements were made in bronze casting, bombards could be made smaller and evolved into bronze cannons.