Rifle Barrel Making: the 18th-century process
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Prior to the development of deep hole drilling, most barrels were made by forge welding a tube and reaming it. (Brass barrels were core castings.) There are several ways to weld a tube but the simplest and one most commonly found on longrifle barrels is a single butt-welded seam running lengthwise. That is what will be described in this article.

The first step is to create a skelp from a bar of wrought iron. The size of the skelp is dependant on the size barrel but for a 46" rifle barrel 1 1/8 at the breech it would be about 38" long, 4"wide and tapering from 1/2 to 3/8 in thickness.


      Barrel making demo for a Learning Weekend in February, 1983

After forging in the desired taper the skelp if "fullered up" (forged in a swage block with a top tool called a fuller that is struck by a sledge) to produce a U shape from end to end.

Beginning in the middle, edges of the skelp are forged over until the contact each other in an area about 2 inches long. This contact area is heated red hot, so it will melt the flux. Flux (can be borax or fine sand) is spooned on both surfaces. The fluxed section is heated to a welding heat (yellow-white hot with a slight shower of sparks) and it is brought quickly from the fire to the swage block. An assistant inserts the tapered tip of a steel mandrel into the tube and quick hammer blows fuse the edges together around the mandrel. The mandrel is only in the barrel a few inches and not for more than a minute so it doesn't usually stick -- if it hangs a little it can be snatched out by catching the hooked handle end on the edge of the anvil.


I usually run at least two welding heats on each section and don't try to weld more than an inch or so at a time. (Some period accounts imply that by using strikers with sledge hammers a team on men could weld several inches in one heat.) Welding is as much art as science and it is important to learn the feel on the heat so you can tell when the weld is sound. I found that getting a round hole during the welding saved a lot of time reaming so I began forging the tube down around a smaller mandrel after the first welding heat.



We pause to examine the weld before returning the barrel to the fire.

I weld to one end then turn the barrel skelp end-for-end and weld the other half. Since the skelp was tapered the resulting tube is heaviest at the breach and has a fairly even taper. I use a concave top swage to smooth up the round tube and adjust the taper as needed to remove any lumps. If a section is undersize to can be enlarged by "jumping" (heating a section and striking the end of the tube on the anvil to thicken the hot part. The flare at the muzzle is also produced by jumping.

After rounding up the tube it is examined for tight spots. If there is any constriction of the bore at this stage the round tube can be reamed with a couple of bits before it is hammered octagon.

I first forge the octagon with a hand hammer at a bright red heat. No swage block is involved in this step--just the flat of the anvil. This is an opportunity to check for welding flaws because they will show up as shadows in the tube. Once the rough octagon is formed, the octagon is refined with a tool called a flatter. The flatter has a flat face about three inches square and is struck by a sledge. Keeping the heat at a dull red during this step will develop a smooth surface and the corners will be sharper. 

UPDATE: American Pioneer Video has released a one hour and 25 minute video showing the barrel forging process described here. Jon Laubach, his son Chris, and Mike Miller are featured. See Jim Wright's web site at http://www.americanpioneervideo.com/ .



This barrel reaming machine was based loosely on drawings in "The Gunmaker and the Gunstocker" by P.N. Sprengel, Berlin, 1771 [translated and reprinted in Journal of Historical Armsmaking Technology, Volume III, 1988]

Reaming the barrel begins with a bit that just touches the tight spots and progresses with larger and larger bits until the barrel is free of any forged surface. These rough boring bits are a twisted square that look a bit like a modern bolt removing tool called an "easy out." They are turned in the barrel opposite the way they are twisted so they don't thread themselves into the barrel and break off. This causes the chips to be pushed ahead of the bit and requires us to stop frequently to blow out chips and oil the bit. If a particular caliber has been ordered it may take even more reaming to get out near final bore size.


Many sizes of boring bits are required.


These three bits would all be turned clockwise.


The barrel is straightened as well as possible during the reaming by removing it from the machine and looking through the bore. A line of light and shadow reflecting in the bore will show the bends.

Once the barrel is close to size the final reaming is done with s single long square bit that is backed on one face with a thin sliver of wood -- flat on the side against the bit and rounded to match the radius of the barrel on the other. Only two corners cut. This bit takes a very light cut and it is "expanded" by placing thin paper between the bit and the wooden backing strip. This reaming is always done from breach to muzzle and after the final reaming the bore will have a very slight taper due to the wear and compression of the wood. 


Two views of the square reamer and its wooden backing strip. Only the two corners opposite the hickory strip cut. As Wallace said in the Gunsmith of Williamsburg film, "the borings are as fine as face powder."



Next the barrel is checked for final straightness and bent as needed. It is then filed to the desired external taper and flare. The flats are filed in opposite pairs. For example, the top and bottom flats first, then the two side flats, then the other four. Once a pair is done several rings can be filed around the barrel at intervals to speed up matching the diameter at each point. Rough filing can be across the flats but the final filing is by "draw filing"-- holding the file at 90 degrees to the barrel and cutting on the pull stroke. Slight irregularities are detected by running the file lengthwise along the flat.

Rifling is simple because the machine controls the process. Rifling is also done beech to muzzle so the groves will follow the taper of the bore. I use round bottom groves. The cutter is pulled through all seven groves, one at a time, until it stops taking a cut , the it is expanded by placing a thin paper shim under the cutter. This is repeated until the desired grove depth is reached. For a patched round ball the rifling is usually about .012" to .014" deep in a hunting rifle. 


This machine was built in the 1980s. The frame is oak but the guide and head block are sugar maple for better wear resistance.



Note the numbers cut on the guide to help track which groove to cut next.


Four tooth rifling cutter inlet in a bore diameter hickory rod.


Thread the breech, plug it, drill the touch hole and try to blow up the barrel by proof testing it. A period proof load (in England) for a forged wrought iron barrel was one patched ball and an equal weight of powder. (About what some bench shooters use every day!) In France it was two balls and 1/2 a ball weight of powder.

I recommend buying the video The Gunsmith of Williamsburg. It was made in 1967 and does not have all the steps we developed later but it will show you how a barrel is welded, reamed, and rifled.


Jim Wright of American Pioneer Video has also produced a new (2009) DVD that shows the forging  in more detail. Jon Laubach did the forging with the help of his son Chris.