Ever since lead was banned for waterfowl hunting, gunmakers and gunsmiths have been modifying chokes, barrels, and other aspects of shotgun technology to work well with nontoxic shot. Rob Roberts of Rob Roberts Custom Gunworks in Batesville, Arkansas, has shaped the modern waterfowl gun as much as anyone. His collaboration with the Benelli Performance Shop has helped influence the appearance and performance of today’s waterfowl guns.
Roberts is quick not to take all the credit. Everything he’s done to guns has been done by others as well. “We didn’t invent the lightbulb,” Roberts says. “What we do is test and test and test to see what works.” Roberts’s company owns two of only six computerized shotshell pattern analyzers in existence, and they make extensive use of them. Here is some of what Roberts has learned.
Roberts is best known for choke tubes. His Triple Threat line (T1, T2, and T3) eschews traditional choke nomenclature for a reason. The performance of standard choke designations like modified and full is often measured by the percentage of pellets within a 30-inch circle at a given distance, but that doesn’t always tell a useful story. Roberts looks at patterns, not percentages. “I don’t care if you get 100 percent of your pellets in the circle. If they are all in a tight clump, you’ll either miss a bird or blow it up,” Roberts says. Instead, he evaluates patterns by their degree of evenness. He wants patterns that spread pellets across the 20- or 24-inch core of a 30-inch circle such that anywhere that core is overlaid on a duck, it will put several hits on target.
Traditionally, waterfowlers wanted the tightest chokes possible. That made sense in the days of lead shot, when ammunition didn’t pattern as efficiently as it does today. Modern hunters benefit from less constrictive chokes and more even patterns. “Someone who doesn’t shoot a lot will be more successful using an efficient choke tube with a more open constriction, like a T1, which is roughly equivalent to a skeet constriction,” Roberts explains. For more experienced shooters, he recommends a T2 choke (similar to light modified), which will shoot even patterns in the 25- to 45-yard range. The T3 (more or less improved modified) is specifically a long-range choke.
Bores and Forcing Cones
The dimensions of a shotgun barrel’s main bore and forcing cone affect patterns as well. Although there is some variation, 12-gauge bores typically measure around .729 inches. Gunmakers have experimented with larger and smaller bores. For a time, aftermarket backboring (enlarging) of barrels was popular. Roberts doesn’t backbore, but he says he has found that bores that are either larger or smaller than .729 seem to pattern best. “I’ve had good luck with barrels around .720 and .740,” he says.
The forcing cone, which is the tapered transition between the larger chamber and the bore, is a crucial dimension, according to Roberts. Traditionally, forcing cones were short and abrupt, and they functioned well with fiber wads. The advent of plastic wads has allowed gunsmiths to relax forcing cone dimensions. Roberts believes a longer forcing cone polished to a gradual taper of about three inches is ideal. “Lengthening the forcing cone takes some recoil off your shoulder, and it smooths the transition from the chamber to the bore, bringing stray pellets back into the pattern,” he says.
Ammunition is a key part of the system, and Roberts believes steel shot has improved a great deal since the early days. “I think the powders are more consistent and cleaner and the wads are better,” he says. Extensive testing has proven that high-velocity shells don’t always pattern as well as slower ammunition. “Sure, speed kills, but patterns kill more, and patterns are what high-performance duck guns are all about.”