The choke on a shotgun is essentially like an adjustable nozzle on a garden hose. Open the nozzle up and it produces a wide spray pattern. Tighten it down and it creates a focused stream of water. By changing chokes shotgunners can do the same with their shot charges. Choosing the right choke and load for the task at hand can go a long way toward improving your wingshooting accuracy and results. Traditional measurement in choke determination is calculated as what percentage of the shot charge is placed within in a 30-inch circle at 40 yards. A load at 70 percent is considered Full choke; 60 percent is Modified; 50 percent is Improved Cylinder; and 40 percent is Cylinder choke. Interchangeable choke tubes are also available in Extra-Full (a favorite with turkey hunters); Improved Modified (patterning between Modified and Full); Skeet II, which is sometimes called Light Modified; and Skeet, which was designed to produce a 30-inch pattern at 25 yards for that game.
By using the interchangeable choke tubes that dominate the current crop of smoothbores, gunners can dial in their pattern for anything from close-range quail to a distant duck to a gobbler’s head at 25 yards. While the denotation on the choke tube is a guide, there are factors that can alter the percentage patterns it produces. The harder the shot, the tighter it will pattern. Copper, or nickel-plated shot will pattern tighter than an equivalent load of soft lead shot. Steel or tungsten/polymer shot will pattern even tighter. Larger shot sizes normally pattern more tightly than smaller sizes of the same shot hardness.