Gunsmithing: Shotguns. Patrick Sweeney

      The shotgun shell was developed to hold a large amount of black powder. When smokeless arrived, the wad had to be changed to take the extra space left by the new more-compact powder. When steel shot arrived, there was plenty of room to adjust again.

      Americans did not take to the pinfire in anything like the numbers that the Europeans did. I think it was the emphasis on breechloaders and ammunition capacity that crimped the pinfire's style. As much of a genius as John Browning was, I think even he would have thrown up his hands if Winchester had insisted on pinfire shells for a repeating shotgun. And if the ammunition companies were going to make centerfire shotgun shells for repeaters, then the makers of American doubles would just have to adapt to them. On both sides of the Atlantic, the pinfire was on the skids even before the next revolution, smokeless powder, came along.

      Successfully developed by the French for their military rifles, smokeless powder was a wonder. It was compact, powerful, and produced hardly any smoke. It revolutionized military rifles and cartridges. In less than a generation, every major power and most of the minor ones had switched to a smokeless, magazine-fed, repeating rifle as standard issue. In the same time, many shotguns were blown up, and countless owners injured, maimed or killed. You see, black powder had some nasty habits, in that it was a low-grade explosive and could detonate in open air. A flame, spark or shock could set it off. But, used in a firearm or cartridge it had the comforting condition of being bulky for its power. You could hardly stuff enough black powder into a cartridge to make it hazardous to shoot. Black powder could be measured by volume, and the bullet or shot charge used to compress the powder on seating.

      Smokeless powder is not an explosive but a flammable solid. In open air it burns fiercely but will not detonate. It is much more dense than black powder, and much more powerful. If you took the volume suitable for black powder in a cartridge and filled it smokeless, you would have created a bomb. Shooters and reloaders who were used to black powder had a difficult time creating enough fillers to take up the space difference. Powder manufacturers even developed special semi-smokeless and smokeless powders that were high-bulk and could fill the powder space in shotshells.

      Even this was not enough for some shotguns. For centuries barrels had been made by the Damascus method. Two pieces of metal, one each of iron and steel, would be heated and hammered flat. The iron could be a common grade of scrap iron such as reclaimed horseshoe nails. (Could I make this up?) In an age of horse-drawn everything but railway carriages, leftover bits of horseshoe nails were common. The steel could be a good Swedish or German steel, or any tough and hard steel. The two flattened and clean pieces would be laid together, and the real hammering would begin. Heated and folded, heated and folded, the steel and iron would be layered many times, like a pie crust. Eventually the layered metals ended up as a rectangular bar. The bar was then heated and twisted in a spiral (with a lot more hammering) around a steel rod called a mandrel. As it was twisted the edges would be “welded” together. I use quotes because that was the term used at the time. The edges were actually forged together. The mandrel was then slid out of the finished tube. Once cool, the tube was filed, polished, reamed and turned into a barrel. For its time, and when used with black powder, a Damascus barrel was quite strong. For those who like the looks, it was also beautiful. The swirling, repeating pattern of the iron and steel would take blueing differently, and the pattern was obvious to any who saw it.

      The pattern is also the weak point of Damascus. The edge between the iron and steel is a joint. Rust has a way of attacking joints. The joint is also weaker than the iron or steel even if it isn't rusted. The burning rate of smokeless powder created two problems for Damascus barrels. The peak pressure of smokeless is greater than that of black powder, and the rate of onset (the steepness of the upwards curve to the peak) is much faster. Smokeless hits harder and comes on faster than black powder, enough so that damascus barrels can rupture. Even if the pressure peak is kept down to that of black powder, the rate of onset is too quick and can still rupture a damascus barrel. The lesson learned then, and one that holds true today, is do not fire smokeless shells in a Damascus barrel.

      To speed up the process, manufacturers looking towards mass production instead took a long flat section of mild steel (it was all mild steel in the 19th century) heated and fed it into a forge. The forge would stamp the steel into a “U” which was then finish-forged over a mandrel and the single seam “welded” shut. Much faster and cheaper to make than Damascus, it also produced a barrel more amenable to lathe-turning to final shape. Not until deep-drilling of steel rods became common did shotgun barrels lose their seams. In deep-drilling, a steel rod is drilled its length, and then reamed and polished to produce a barrel blank. Compared to the earlier forged barrels, a drilled barrel is absolutely uniform as a produced item. That uniformity greatly aided the development of reliable and safe breech-loading mechanisms. The new steel barrels were often referred to as “fluid steel” barrels. Not because the steel was more flexible, but because it came out of the crucible liquid, and was poured into molds to make ingots that were forged into bars, rods, rails and I-beams.

      Damascus had been the mark of a fine gun for so long that some makers would take their new and stronger fluid steel barrels, and etch a Damascus pattern onto the outside. And you thought appearance for appearances sake was a late-20th century innovation.

      While the strength drawbacks of Damascus eventually led to its demise as a barrel steel, the American emphasis on mass-production would have put the skids under it even without the advent of smokeless powder. (Damascus does seem to be making a comeback as a knife blade material.) As if the weakness wasn't enough, producing a Damascus barrel was more expensive. The many thousands of hammer blows it took could only come from a skilled worker, and his output was limited to a few barrels a day. Once created, the Damascus barrel had to be hand-filed, bored, reamed and polished. The iron and steel were each of a different hardness. Trying to turn a Damascus barrel on a lathe as a production process would have been a nightmare. With orders for thousands of shotguns, Winchester, Remington, Savage and the other large manufacturers could not even consider making barrels from Damascus.