Middle Era

Part 12 - Gun Making

The Chinese at first made fireworks and small gun barrels from bamboo tree trunks. They were often tightly wrapped with rope made from bamboo fibres to prevent them bursting. Larger gun barrels were made of cast iron, bronze or brass using sand or clay molds. 

 Later Chinese and early European gun barrels were made of wooden staves held in place with wrought iron hoops. Precisely the technique used to make wooden barrels, hence the name. They were often reinforced with wire or leather wound around the barrel. 

In the 14th century, blacksmiths made small barrels with flat iron bars fitted tightly around a cylindrical wooden rod and held in place with hot iron hoops that contracted when cooled, thus forming a rough tube, The blacksmith then heated the tube to a white-hot forging temperature that allowed the strips to be hammer-welded together. For smaller barrels, a blacksmith would bend a flat bar into a tube and then hammer the long single seam to forge weld it few inches at a time. Alternatively, blacksmiths coiled iron or steel strips around a round rod to form a helical tube known in France as a "Canon a Ruban" (ribbon cannon) before forge welding the overlapping coils. The tube wall thickness at one end of the tube was often increased by heating it white hot and striking the tube at one end. The bore (inside diameter) of the tube was then drilled, or more commonly reamed, to a smooth true cylindrical shape. To ream the tube, a blacksmith or gunsmith pulled cutting tools through the bore before polishing it with smooth grinding stones.

The best guns were made from "Damascus Steel" (wootz steel) that was developed in Southern India around 300 BCE for sword blades. But the technique of forging strips of cast and wrought iron together, by repeated folding, heating, twisting and hammering, was used by the, Chinese, Vikings and Celts from 600 CE. The blend of low carbon wrought iron with high carbon cast iron produced laminations of medium carbon steel that could be hardened and tempered to make hard, tough cutting edges. To make heavier cannon, pattern makers made an exact copy of the final casting in wood, clay or wax and placed it in a two-part molding box before packing it with sand. They then baked the box, to dry the sand, before removing the pattern. Afterwards, they reassembled the two parts of the box and poured molten metal into the cavity left by the pattern. For smaller casting Chinese blacksmiths used the lost-wax method where the pattern was made of wax. When baked, the wax melted and ran out of the mold before the molten metal was poured in.

But early casting technology was plagued with problems. The metal was often impure and not homogenous (uniformly blended) and the casting was typically cooled unevenly causing de-lamination and stress cracking. To compensate, early gun barrels were made with thick walls to withstand the shock of repeated explosions.

Early gunners poured gunpowder into the barrel and rammed it tightly with a ram rod before adding a lead or cast iron ball that was slightly smaller than the bore of the tube. This allowed for the build up of gunpowder residue after repeated firing. Periodically the residue had to be scraped out and the barrel cleaned.

The gunner ignited the gunpowder with slow match, a piece of string containing chemicals that burned slowly. He had to set fire to the small amount of gun power poured into a flash-pan at the touch hole near the end of the gun. This was relatively easy for large guns but musketeers had to aim the gun while watching the touch hole and the slow match.

Invented in the 15th century the matchlock made firing a hand-held gun easier. A trigger mechanism moved the slow match to the flash-pan so the musketeer could concentrate on aiming the gun.

Early guns were inaccurate, except at close range, and the slow process of reloading after each shot meant cavalry could often annihilate a line of infantry while they were reloading.

When Henry VIII became King of England in 1509, he found very few guns in his arsenal and only one cannon maker in all of England, so he quickly importing every gun he could buy from continental Europe. When Henry placed a large order of guns with the kingdom of Venice in 1513, just before a war with France, the Doge of Venice received a report from his outraged ambassador complaining that Henry already had, "enough cannon to conquer hell!"

Because of the monopolistic power of local guilds throughout continental Europe, many skilled gunsmiths were no longer allowed to practice, so Henry VIII invited some of them to England and set them to work around the Tower of London.

The flintlock firing mechanism was developed early in the 17th century. It used a trigger to release a spring driven piece of flint that showered sparks onto the flash-pan and it rapidly replaced earlier firearm-ignition systems like the matchlock and the wheel-lock. It remained in use until the mid 19th century when it was replaced by the percussion cap.

Until the 15th century, all guns had been smooth bore but archers knew that arrows flew more accurately if they spun, so German crossbows makers shaped the arrow head, angled the feathers or passed the arrow through a tube with helical grooves. This idea was transferred to the gun, and the rifle with a helically grooved bore was invented in Germany, possibly by Augustus Kotter of Nuremberg in 1520.So while British soldiers were using the smooth bore Brown Bess until the 1850's, German armies were using rifled guns by 1631. Most infantry officers disliked rifling because it was harder to clean gunpowder residue from the fine rifling grooves.

During the American war of Independence, British troops discovered that the Kentucky long rifles, made in Pennsylvania by German immigrants, were far more accurate than their Brown Bess smooth bore muskets and could kill from a greater distance. Allegedly, after he'd won the battle of Waterloo, the Duke of Wellington prevented the adoption of rifled guns by the British and it was not until shortly after his death that British troops were equipped with Enfield rifles.

Like other muskets, the Kentucky rifles were muzzle-loaders as these were cheaper to manufacture. The round lead bullets were a size smaller than the barrel diameter, but were wrapped in greased cloth wadding to provide a tight fit in the barrel. The rifle barrels had 7 to 8 spiral grooves cut into them and they were accurate to at least 400 yards (365 m), although skilled marksmen could hit targets at a range of 800 yards.

Thomas Jackson Rodman (1815–1871) was an American general and gun designer who developed a series of heavy 8-inch, 10-inch, 13-inch, 15-inch, and 20-inch bore guns intended for seacoast fortifications. The Rodman guns were hollow cast, an innovative method of casting iron gun barrels that produced guns much stronger than traditional cannon, designed to fire both shot and shell.

Instead of the tradition molding box, the pattern was installed vertically, with the muzzle pointing up in an iron cask. The bore of the gun was formed by a cylindrical cooling tank placed into the cavity after the pattern had been removed from the flask. The flask was then heated from outside by a fire while the cavity was filled with molten iron. The casting was carefully cooled by water flowing through the tank while the outside of the casting was kept hot by the fire.

Traditionally, guns had not been cast as hollow tubes, instead, the bore had been drilled out of the casting. Also, the casting had been allowed to cool from the outside which meant that the outside contracted and solidified while the centre was still molten. And, as the centre cooled it shrank away from the outside thereby seriously weakening the gun barrel. Rodman's ingenious solution was to cool the casting from the inside so the outside would solidify last and would thus contract to compress the inner surface.

After days of slow cooling, machinists bored the gun to the finished inside diameter, turned the exterior smooth, finished the trunnions on a trunnion lathe, and drilled a vent (touch hole).