Shooting

A swarm of shot pellets in the air does not expand in the straight- sided cone that’s typically used to illustrate it. A shot swarm expands in a bell-shaped pattern, constantly enlarging at the edges. Nor does it travel as a pancake, with all the pellets flying in the same plane. As in any organized collection of moving objects, there are leaders and followers. In other words, a shot swarm strings out. How much the tail end of the swarm falls behind the leading edge depends upon the load, in terms of the number of pellets, the height of the column, the bore diameter and the propellant that starts them on their way.
Of all the dimensions of a shot swarm’s behavior in the air, stringing is the most difficult to determine. It can’t be measured on a pattern plate, because all the plate can show is the two-dimensional end result. That can tell us height and breadth and ultimate density, but it can’t show the dimension of time, of how long those pellets took to get where they were going. Stringing is time and distance—the third dimension of the shot swarm.
In practical terms, it also is a function of motion. You can only get a real sense of stringing by shooting something that’s moving. In the 1890s some enterprising Frenchmen thought of dropping iron plates from the Eiffel Tower while someone shot them on the way down. Didn’t work; terminal velocity was so fast that no one could hit them. Not long after, some Englishmen fastened plates to the sides of railway cars. That worked a bit better, but the results were inconclusive at best.

Much later, a couple of engineers from the University of London devised a pattern plate comprising one-inch squares, each wired to a computer that measured the time lapse between the first strikes and the last ones. Their findings were fascinating but still inconclusive. Extrapolating time to distance is the key to learning just how long a shotstring can be and what it’s like in profile.
It remained for a Texan, my old friend the late Bob Brister, to demonstrate the phenomenon once and for all. There’s a whole chapter about it in his great book Shotgunning, the Art and the Science. Essentially, he fastened a couple of plywood sheets, 4 x 8 feet, end to end onto a trailer, hitched it to his Suburban, and had his wife, Sandy, drive past at varying distances going 40 mph while he blazed away with various guns and loads. It was time-consuming, labor-intensive work—marking the pellet strikes after every shot, photographing the results, changing the pattern paper and starting over. It must have been a bit hair-raising for Sandy at times, though by then she was well accustomed to Bob’s experiments, and she did tell me that she kept the windows tightly up.
The findings proved what logic would suggest—that shot columns disproportionately long in relation to bore size string out more than others. The 3" .410 is one, the 3" 20 another. The 3-1/2" 12-gauge didn’t exist then, but I’m sure it would fit the pattern (no pun intended).
The reason for this is perfectly simple. The only way to increase the shot charge in any given bore diameter is to stack the shot column higher in the cartridge. The longer the column, the greater the distance between the pellets in the front and those at the rear, so the longer the string is going to be. It’s simple physics: If the whole charge leaves the muzzle at the same speed, does it make sense that the rearward pellets are somehow going to speed up and join the others? The phenomena of slipstreaming and drag (in some venues called “drafting”) tend to compress the string a bit—not because the ones behind speed up but rather because the leaders, breaking trail through the atmosphere, tend to slow down at a faster rate. But they all begin to slow as soon as they leave the muzzle, so it’s a relative thing. Shot charges string out, and that’s the fact.
In blackpowder days stringing was a great problem. Being semi-explosive, blackpowder deals a brutal blow to a shot charge upon ignition, crushing the pellets at the base of the column. Then the circumference of the column scraped against the barrel wall, deforming still more pellets. Round objects are not aerodynamically efficient to begin with, and the ones compressed or scraped lopsided are nearly useless; they either spin away from the main swarm as flyers or lag far behind. Either way, they contribute nothing to efficiency. All gunmakers could do was polish bores mirror-bright to reduce friction. It helped, but not much.
During the period of transition between black and smokeless powder, shotstrings probably grew a bit shorter, but even early smokeless didn’t shorten them significantly. The first real improvement came in the early 1920s, when John Olin’s Western Cartridge Co. introduced Super-X cartridges loaded with the new progressive-burning powder. These powders pushed shot charges rather than blasted them down the bore. Less-violent treatment meant less deformation to the pellets.
Next came the process of alloying pure lead with antimony, which made the pellets harder—again, less subject to deformation.
The real breakthrough was Remington’s introduction in 1960 of the Power Piston wad. Made of polyethylene, the little device was everything a shot charge could want. The collapsible base cushions the bottom pellets as the powder ignites; the thick shot cup protects the whole column from abrasion on its way down the barrel. Within a few years, every ammunition maker had its own version, and they all seemed to work equally well.
In studying the shot cup’s performance in the early ’60s, Winchester inadvertently captured at least a portion of a shotstring. Using high-speed photography, the company wanted to show how the cup petals peel back from the shot swarm. Photos shot a foot or so out of the muzzle clearly show the wad shedding away. They also show the beginning of a string, with the tail-end pellets decidedly behind those in the lead.
With the combination of progressive-burning powder, harder pellets and better shot-cup wads all packed into a plastic case, the modern age of shotshells arrived. But it didn’t eliminate shotstringing. It made strings a lot shorter, at least when they aren’t overly long inside the case. The more nearly the height of the shot column matches the diameter of the bore it’s to be fired through, the more efficient the pattern will be. This is known in parlance as a “square load.” To use a good example, it’s why the 3/4-oz 28-gauge is so good. There may not be a zillion pellets, but they all reach the target in a very short time, and that’s a lot of energy imparted. There are optimal shot charges for all of the gauges, and they create optimally short strings. The larger the bore, the more flexibility in what works efficiently, but there are limits that cannot be exceeded without crossing the line into the land of diminishing returns.
Some have argued that long strings are actually an advantage, that if the front end of the string passes in front of the target, those pellets in the center or even at the end surely will get the job done. It’s certainly possible to miss in front; I see it occasionally in schools, though not very often. But to think of a long string as some panacea? File that under Wishful Thinking.
Better to have a short string and put the shot where the bird is.

Michael McIntosh is the author of such books as A.H. Fox, Wild Things, Best Guns, Shotguns and Shooting and More Shotguns and Shooting. His new book, Shotguns and Shooting Three, will be available this fall.