Every shot pattern has clumps of pellets here and gaps there. While the “perfectly distributed” pattern might be a myth, you can maximize the efficiency of how your gun patterns for specific purposes. Spending some time experimenting with chokes and loads at the range will help you find the perfect pattern for your own needs.
Shotshell patterns are traditionally tested by shooting paper targets at 40 yards and evaluating pellet strikes within a 30-inch circle. The 40-yard distance is useful but arbitrary. Do your testing at whatever distance you typically shoot or, if you want to be really thorough, shoot patterns at five-yard intervals starting at 20 yards and ending at 50. That said, a 30-inch circle represents the approximate maximum useful size of a shot pattern, so use that as your standard. Shoot a minimum of three shells at each distance with each choke/load combination that you’re evaluating.
Look at the pattern from each shell and draw a 30-inch circle using the densest part of the pattern as the center. You’re looking for patterns that are concentrated in the center yet also have enough pellet strikes within the circle to provide some margin for error. For most shells that means a 75–80 percent pattern at whatever range you’re shooting. To estimate pattern percentage, count the number of pellet strikes within the 30-inch circle and divide it by the total number of pellets in the shell. As a rule of thumb, look for a pattern that puts 100 to 110 pellets in the circle for big ducks or 70 to 80 for geese. Eyeball each pattern to see whether the pellet strikes are distributed somewhat evenly.
If you are patterning stacked loads, take note of where the larger and smaller pellets strike the paper. Some stacked loads combine large steel with smaller bismuth or TSS shot, with sizes matched to be more or less ballistically equivalent in terms of energy. To me, this means that it doesn’t matter if a hole is large or small, just that there are enough of them overall and that they are spread across the paper in a useful fashion.
Stacked steel loads, which contain larger and smaller steel pellets, are designed to increase energy on target. For a stacked steel load to be effective, it should be putting the bigger, harder-hitting pellets into the center of the pattern.
Regardless of the type of load you are testing, if there are too many pellets in the core and not many in the outer fringe, you have a pattern that’s too tight, and you need a more open choke. If the pattern is so open that there aren’t many pellets in the core and there are gaps all over, you probably need a tighter choke. It is true, though, that patterns of very large pellets sometimes tighten up with less choke.
Changing chokes is one way to improve a pattern. Going up or down in pellet size and velocity can have an effect as well. In general, larger pellets and/or lower velocities produce denser patterns, while smaller shot and higher speeds open them up.
A sheet of paper is a stationary target. As such, it tells you nothing about the length of your shot string. Paper gives you just a 2-D picture of a 3-D phenomenon. With steel, tungsten, or bismuth pellets of a single size, shot strings remain short and hardly worth worrying about. When you switch to shells containing two sizes of shot, or two different materials, the shot sizes will separate at some point downrange. Extended shot strings become a concern on long-range crossing targets, when pellets at the back end of the string may arrive too late. Patterning on paper won’t show you the point where a stacked load strings out. That’s a good reason to reserve stacked loads for short- to medium-range shooting, where they are very effective. If you know that your shots will consistently come at ranges exceeding 35 to 40 yards, you’re much better off choosing a single, larger shot size and finding a choke that patterns it well.
