Gunsmithing: Forging the Barrel
How is heat treatment involved in gunmaking?
Needless to say, very early North American gun barrels were made in Europe and imported to the new world. The demand increased as did the immigrants with gunsmithing skills, allowing rifles to be made in this country. Legend holds that Lancaster, Pa., is the birthplace of the American longrifle.
In order for barrels to be made in the new world, a supply of wrought (forged) iron was needed. Cast iron was too brittle. The starting stock for a gun barrel was wrought-iron skelp weighing over 15.5 pounds.
Once the forge is prepared, the bar is heated. It is fully forged along its length to help refine the metal, giving it better integrity. An anvil is used to begin to form the bar into a round profile. The process of forging the barrel in this way involved heating followed by working the shape a little followed by another reheat, etc. It took about 10 to 12 hours to forge a single rifle barrel.
When the barrel is finally formed to the proper shape, it is ready for welding. Because of the higher heat required during this part of the process, gunsmiths must work very quickly after removing the barrel from the heat. A mandrel is quickly inserted into the hole to keep the bore from collapsing.
Once the weld is completed, octagonal flats are forged onto the end and worked down along the entire barrel, which makes the barrel stronger due to the favorable grain-flow orientation produced by the process. The finished barrel tube weighs 6 pounds, a reduction of more than 9.5 pounds, which is due mostly to scale loss throughout the process. At this point, the barrel is rifled.
What thermal processes are involved in some of the other components of the early rifle? Whether we’re talking about the rifles made in the 19th century or the authentic reproductions of today’s craftsmen, many of the pieces and parts involve thermal processing in their manufacture.
Most of us think of the flintlock as the rifle of this era. In fact, the flintlock was first invented in Paris in 1615. It was the choice ignition system until the middle of the 19th century. Because steel was not readily available in the 18th century, all of the ferrous parts of a gun were made of non-hardenable iron. Therefore, all of the parts of the lock – except the springs – were case hardened to protect them from wear. The early case-hardened frizzens would need to be recarburized in time to provide a good, hard striking surface.
To make a reproduction gun, much of the old-time craftsmanship is still utilized. Purists reproduce the early techniques, which would include forging the trigger and lock and sand casting “furniture” such as the butt plate and trigger guard. Trigger springs are handmade from truck leaf-spring material and are hardened and tempered.
These parts are heat treated using a forge or an oxy-acetylene torch to heat the piece to a red or red-orange color. Depending on the type of steel used, quenching is done in either oil or water. The quality of the hardening process is verified by the file test, which consists of running a hardened file over the part. If the part is not marked by the file, it is considered to be fully hardened.
Tempering is performed by heating to a pale blue color by carefully heating above straw color to avoid overtempering. At Colonial Williamsburg gun shops, parts are tempered by soaking in molten saltpeter (~600°F).
Cast brass would be rolled out to make the patchbox in the stock. True craftsmen will typically buy authentic brass 3/16-inch plate and roll it to about 1/16 inch. The brass will need to be annealed during this process, which is done by heating to cherry red and quenching in warm water. Early gunsmiths would add decorative flair by flattening a silver coin and making silver stars or moons to decorate the stock.
Did you know that some of our present-day terms came from the use and manufacture of guns? The title refers to everything involved in the gun and is used to represent inclusivity. “Flash in the pan” is a term to designate something that is fleeting and very temporary. It comes from an insufficient flintlock spark, which creates only a small flash in the pan. One that was new to me (as a gun term) was the saying “stop dragging your butt.” Tired soldiers on a long march were told this when they became too tired to carry their rifles and began dragging the bottom end (the butt) on the ground.
Now you know how the rifle was made and how it is still crafted by those interested in re-creating some of our early gunsmithing history.