SHOTSHELL EVOLUTION, DESIGN AND PERFORMANCE
Tim Le Cras 2023-03-15 11:23:26
Advances in shotshell design and components have been major over time, and modern-day shells are now capable of breaking targets more consistently and at far greater distances.
Shotshell design and components have undergone huge changes over time. The history of these designs and evolution of the components give us insights into modern-day shells and the forces that influenced these developments. Modern shells have very precise components optimized to deliver consistent patterns and the best possible performance. The journey from the earliest shotshells to the modern-day shells we enjoy today is an interesting one.
ORIGINS AND EVOLUTION
The first shotgun shells were paper packages containing the powder, wad and shot to facilitate the loading of early muzzleloading shotguns. When breech-loading percussion shotguns, like the Sharps, emerged in the 1850s, paper cartridges developed further. These were typically comprised of two parts: a folded paper tube of black powder loaded into the breech and a twisted tube of wadding and shot. The powder tube protruded from the rear of the chamber so that when the breech block was closed, it could be cut off to expose the powder to the flash hole in the breech. While these early shotshells speeded up loading, they were not durable or reusable.
In the 1830s, two Frenchmen, Robert and LeFacheux, developed the pinfire shotshell cartridge, which consisted of a tube and fiber wad and crimped brass head. The pinfire cartridge had a hole drilled in the side of the head and base wad through to the powder charge. A percussion cap was placed under the hole and a brass firing pin fitted through the hole into the cap. Black powder was dropped into the cartridge, and a tightly fitting fiber wad was placed over the powder. Shot was added and a cover wad applied. The brass head on these pinfire shells was shallow and rimless. There were several issues with the pinfire shells, including gas escaping around the pin and the fact that they could easily detonate if dropped. In addition, the shells were expensive, and so were the guns that used them, so they were not used extensively.
There were a number of shotshell designs that came out between the pinfire shotshell and the development of centerfire cartridges, but none were very successful. The Lancaster shotshell emerged in 1853 and had four holes pushed through a copper base disk and a center with priming compound on the outer side. A capsule of thin copper held this together, and when the firing pin struck the copper head, it crushed the head and copper plate, igniting the priming compound and causing flashes through the holes, igniting the powder on the other side. In addition to being expensive, this design was not great, as the copper head and plate usually ruptured — these shells were not reusable. For shotshell designs to become popular, especially in the U.S., they had to be affordable and reusable.
In the 1850s, shotshells with centerfire primers began to be developed, and these soon became popular all over Europe. They did not catch on right away in the U.S. because of their expense. American shooters wanted shells that could be reloaded multiple times. In the 1870s, Maynard of New York developed shotshells with a brass cup and a soldered brass disk, with a percussion cap on a nipple. When struck, a flash came through a small hole in the center of the disk and ignited the powder above. In a second version, Maynard improved his design to be a self-primed shotshell with a hollow anvil riveted into the head. The key advance was that the spent primer could be easily removed. These shells were durable and could be reloaded multiple times. Onepiece brass shotshells began to emerge around this time and were bought and then loaded by shooters. The addition of serrated top and brass fingers to the top of the shell allowed them to be bent in to retain the top wad, but they would break off after extensive use.
In 1877, Winchester began offering shotshells with paper hulls, and then in the 1880s, shotshells that were already loaded. These had a layered paper tube and a shorter reinforcing tube inside with a paper base wad. They also had a low brass head inside the paper assembly and a primer pocket in the brass.
A huge development occurred in the 1880s when French chemists developed smokeless powders. In the early 1900s, factory-loaded shells gained popularity, and new companies arose producing high-quality, reliable shells. In 1912, Remington patented the nitro club steel-lined shotshell with an extended steel head to help eliminate gas blowout and support the more powerful smokeless powders. Noncorrosive primers and powders with higher performance were developed by Remington in the 1920s. Cup wads in the 1930s improved gas sealing, and in the 1950s, plastic shotshells and wads emerged. So, in addition to progressive changes in shotshell designs and structure, the components also underwent major changes. These are discussed later in this article, as improvements in each of the shotshell components has pushed the overall performance of shotshells to modern-day levels.
PRIMERS
When struck by the firing pin, the primer sets off the whole firing sequence by igniting the gunpowder. Primers need to be consistent and need to function under a wide range of weather conditions. Primers in the pinfire cartridge, mentioned earlier, used mercury fulminate [Hg(CNO)2] as the priming compound, as it was very sensitive to shock, heat or friction. However, mercury fulminate had two major problems: It was susceptible to water contamination and tended to decompose with storage, and it left behind a very corrosive residue that caused rusting and corroding of the shotshell case.
In 1928, Nobel developed lead-styphnate (C6HN3O8Pb) primer compound, which is relatively non-corrosive and is the basis for modern-day primers. Modern primer formulation is typically 40% lead styphnate that is the primary explosive component, 40% barium nitrate that oxidizes the chemicals to fuel the explosion, 16% fuels for the explosion, and 4% tetrazine that acts as a sensitizer, making the primer compound easier to ignite. The proportion of these constituents vary from one manufacturer to another, but in general this formula is relatively constant.
The structural design of primers has gone through a number of iterations. In 1866, Berdan patented a primer design that had a soft copper cup with the priming chemical compound in a pocket and two flash holes on either side of an anvil. When the firing pin hit the cup, this pressured the primer compound against the anvil, causing it to explode through the two flash holes and ignite the powder charge above. Around the same time, Colonel Boxer in the British Army developed a different primer cup design with the anvil in the pocket of the case and a single, larger flash hole.
The performance of both types of primers was similar, but the Boxer primer had the advantage, as it was easier to punch out and replace. The three main components of today’s primers are a cup, the primer ignitor compound, and an anvil. When the metal cup gets dented by the firing pin, it causes the anvil to apply pressure to the primer compound, and ignition takes place in 2,000-1,500 microseconds (.002 seconds). The resulting flame and hot particulates penetrate through a flash hole to ignite the powder charge. Shotgun shell primers are constructed somewhat differently than primers used in centerfire rifle and pistol primers — the 209-style shotshell primers have a cup, similar to a Boxer primer, but the anvil is on a pair of legs, and there is a central vent for the flash hole.
GUNPOWDER
Today’s shotshells are loaded with smokeless powders. Smokeless powders are formulated to have different characteristics, and some are used for particular gauges, especially sub-gauge shells. The origins of gunpowder go back a very long way — around a thousand years ago, black gunpowder was developed in China. Black powder was composed of three main components: around 75% salt peter (potassium nitrate; KNO3; an oxidizer) mined from caves filled with bat guano/excrement, 10-12.5% sulfur (to stabilize), and 12.5-15% charcoal (to fuel the explosion). Changing the ratios of the three different components resulted in different burn rates and therefore different uses. Black powder had some major drawbacks: 1) A large amount of solid residue is left and this could quickly obstruct gun barrels; 2) The considerable amount of white smoke produced when black powder ignites would give away the location of the soldier firing the gun; 3) Black powder easily absorbed moisture and corroded; 4) Energy content was low compared to modern smokeless powders, which have about 30% more energy.
In 1846, a German chemist, Schonbein, developed a new type of explosive called nitrocellulose made by treating cotton or other sources of cellulose with nitric and sulfuric acids to change the hydroxyl (-OH) groups to nitro (-NO3) groups, which then decomposes explosively. Around a year later, the Italian chemist Soberno developed nitroglycerin. Alfred Nobel (after whom the Nobel prize is named) figured out how to package this unstable chemical for use as an industrial explosive.
The invention of nitrocellulose and nitroglycerin became the key components of smokeless powders around 40 years later. Vielle developed the first commercial smokeless powder, which he called “Poudre blanche,” white powder, for the 8mm French Label rifle. Poudre blanche was 100% nitrocellulose, burned very cleanly and produced much less smoke and more energy. Nobel patented “Ballistite,” a mixture of nitrocellulose and nitroglycerin, in 1891. Most smokeless powders today use nitrocellulose as a single base or combinations with nitroglycerin from 2-39% making double base powders. Unlike black powder, smokeless powders need heat and pressure to ignite effectively, and so the type of primer is essential. The combination of heat and pressure synergizes to increase the burn rate and resulting pressure. Modern-day smokeless powders also have refinements that affect the grain geometry, surface characteristics and chemical coatings with additives so that it is possible to further control the burn rate and create longer-burning powders. Graphite is sometimes used as an additive to prevent clumping.
WADS
The main function of shotshell wads is to separate the shot pellets and the powder charge. At firing, the wad acts as a gas seal, keeping the expanding gases behind the shot. Wads also cushion and protect the shot from deformation. Early shotgun wads were simple disks made from felt, fiber, leather, cork or cardboard. In the 1960s, plastic wrappers began to be used — these were initially just flat sheets of polyethylene and protected the pellets from contact with the bore, although fiber wads were still used. Plastic shot cups came in later. Before too long, plastic wads began to replace cardboard wads. They had skirts to create a better seal against the barrel wall and prevent gas blowby. These developed even further to include an integrated skirted base, pellet cushioning collapsible spacer, and cup section to hold the shot, and these wads were easier to load. The pellet cup section also reduces lead buildup in the bore and usually has slits so that it opens as it exits the barrel and releases the pellets. Wads differ in size based on what gauge they are used for and also the load that they are designed for.
LEAD SHOT
Shotshell pellets made of lead are relatively soft, and this reduces damage to the barrel of the shotgun. Lead shot was originally made in molds or by pouring molten lead into a water barrel. William Watts patented the process of making superior lead shot using a tower in England in 1782. This type of tower-dropping method, which is still in use today, starts by melting ingots of lead. This molten lead is then poured through a copper sieve, with holes that determine the size of the shot. The resulting molten lead spheres fall down the tower into water at the bottom to complete the cooling. The height of the shot tower limits the maximum size of the shot that can be made.
In 1849, the LeRoy company in New York patented a new method called “wind tower”, where a blast of cold air cooled the shot quicker, so the tower did not need to be as tall. In the 1960s, the Blumeister method was developed to generate smaller shot sizes. Larger shot can also be made by stamping lengths of lead wire with hemispherical dies.
Lead shot usually contains antimony and a small amount of arsenic. Antimony is added to harden the lead alloy. Arsenic is added to improve the spherical nature of the shot. There are two main types of shot produced today. “Chilled shot” is softer and denser, as it only contains around 0.5-2% antimony. Chilled shot deforms more readily when it hits a target, transferring the energy. Magnum shot has a higher antimony content, usually 4-6%. It is harder and so deforms less, retaining its spherical shape and patterning better. Shot can also be plated with copper or nickel to coat it with a harder jacket and so reduce deformation.
HULLS
Early shotshells were made with full brass casings. These were reliable and reloadable. Around the 1870s, paper hulls began to be used, with the paper often waxed or coated to improve its durability and weather resistance. Paper hulls were used for almost a century. In the 1960s, plastic hulls began to appear on the market, and by the 1980s, most hulls were made from plastic. Plastic hulls are easy to reload, which is a big advantage. Brass or steel bases are still needed on plastic hulls, and more powerful powder charges usually come with higher brass. Early shells also had wads at the top of the hull to keep the shot in place, but with the transition to paper and then plastic, they could be crimped to hold in the shot at the top. Of course modern-day plastic hulls usually have six or eight petals that make up the crimp.
FUTURE ADVANCES
What does the future hold for shotshells? The quality and types of components will likely continue to improve, and design modifications are also possible. Reductions in felt recoil, with so called “softer-recoil” shells, are becoming more common these days. Lower-recoil shells usually come from using lower powder loads or more collapsible wads that absorb and spread out the energy of the explosion.
▶ Tim Le Cras is a freelance writer and photographer and a FITASC referee based in Cincinnati, Ohio. You can contact Tim at timdlecras@gmail.com
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