"From a flat bar of soft iron, hand forged into a gun barrel; laboriously bored and rifled… in a shop long since silent, fashioned a rifle which changed the whole course of world history."
— Captain John G. W. Dillin, The Kentucky Rifle
How, since the 15th century and right up to the American Revolution, did weapon manufacturers drill a hole in an iron barrel flawlessly straight and over three feet long? And how was the hole maintained so perfectly parallel to the axis of an iron rod, that when a bullet was launched, it flew true to its target? The answer was not drilling, but boring. With a drill machine, the workpiece was held still while the material was penetrated. Whereas a boring machine moves the workpiece against the milling cutter, hence a boring mill, both hand or water driven.
The technology of shaping a gun barrel with a precise and centered hole, primitive as it was, by the 18th century, became a discipline of meticulous and time intense mastering. It had flourished to produce some of the most accurate weaponry of precision; one of the finest examples – the Kentucky long rifle. Replica testing at Colonial Williamsburg Virginia proved these rifles produced a bore to diametral tolerances within 0.0005 of an inch; all by hand! Comparable to the accuracy of today’s complex machinery, it is mind boggling. As gun experts will tell you, ‘it can’t get much better than that.’
How gunsmiths and blacksmiths ended up with a near perfect hole in a long tube of wrought iron involved the same basic principles that allowed Alexander the Great’s armorers to crank out spears and swords; heat and hammer. Add to that an ingenious twist of a rotating boring mechanism, and the result was a weapon that could hit a squirrel from a branch at 200 yards.
Two-Step Process With a Third Step if to be Rifled
Prior to the American Revolution and on into the 19th century, wrought iron was used in the barrels of muskets and rifles, whereas cast iron and brass were used for cannon; later wrought iron was used for the breech and by the 1860’s, the whole cannon. Steel (induced carbon to wrought iron in a closed furnace) and case-hardened iron (by the amount of slag in the iron) formed working parts of the gun; such as trigger and guards, springs, flint mechanisms, etc.
If only one tool was used to both make and expand the hole in the barrel, it would be less precise. The process of hand manufacturing a gun barrel before the advent of gas and electric driven machinery was basically a two-step process. Three steps if the barrel were to be rifled.
- First the barrel was fashioned from flattened wrought iron that was hammered and wrapped around a steel rod to precent the tube collapsing. When the rod was removed, the result was a hole in the center that would be smaller than the finished hole.
- Secondly, the hole was enlarged, cleansed, and polished through precise boring to fit the caliber of a particularly sized shot or bullet.
- For rifle barrel, it required the additional boring of grooves along the inside tube called ‘rifling.’ This set the bullet spinning as it was launched. This stabilized the shot to assure better accuracy.
First Step: Forging, Hammering, and Welding the Barrel Around a Rod or Mandrel
The gunsmith master and his journeyman heated a long piece of wrought iron in a forge. Wrought iron was produced by smelting pig iron and oxidizing it; subjecting it to heat and stirring it in a furnace without using charcoal – called puddling. Wrought iron has little or no carbon, and has varying amounts of slag; a larger amount of slag produces case-hardened iron. Slag are silica inclusions running through the iron somewhat like the grain in wood. The wrought iron was hammered into a long and flat rectangle called a skelp (also blank or plate) whose thickness was a little greater than the wall thickness of the finished barrel. They would flatten any number of these longitudinal single sheets to form the barrel.
A flattened wrought iron skelp (blank or plate) ready to be hammered to form a gun barrel tube.
The flattened skelp was laid on a swage block which is anvil-like, but with multiple groves for shaping and molding. Swage blocks were of cast hardened iron or steel. Once the iron reached a workable heat, it was removed and placed on an anvil.
The skelp was hammered onto the molding swage, bending in the center and curving up the sides. The flat iron skelp was then shaped into a tube by hammering and beating while rotating it to wrap around an inserted steel rod or mandrel. The steel bar is to keep the bore from collapsing as you hammer. Several reheats were required throughout the process, during which care was taken to keep the steel mandrel at a lower temperature than the skelp; this to prevent it from being welded in place. The iron was continuously re-heated and hammered until a long barrel was produced. Rifle barrels were hammered into a rough octagonal shape. The look was popular and the sides were simpler to forge when working with a heavy tube.
According to master gunsmith Wallace Gusler of Colonial Williamsburg, Virginia, “It doesn’t have any practical use; just style.” However, when finishing the barrel in later stages of the process, gunsmiths could only draw file long surfaces flat, necessary to remove rough forging marks, giving the rifle its highly preferred finish.
Seams were Forge welded. Prior to forge welding or fusion of the edges that formed seams along a continual iron tube around the steel rod, flux was sprinkled on the seams. Flux is made of borax, iron filings, and sand. It melts over the seem to keep scale from forming. Scale is a layer of oxide on the surface that prevents the iron to bond in forge welding. The barrel was heated to the fusion point. The master only has a few seconds to hammer fast and moderate in weight to fuse the two edges together. Metal is very hot and if hammered too hard, it will be too thin.
Master welder Wallace Gusler says that when forge welding, he “
Judges the heat strictly by eyesight and hearing. You can hear the hissing of the metal when it is at the fusing point. At the right temperature you also get a lot of white sparks flying from the iron as you hammer.”
