Maximum Shotgun Range

A number of factors determine the maximum effective range of a shotgun, with gauge, choke and the load used being the most influential. However, there are some things about scatterguns that defy explanation, and they will long cause ballisticians to scratch their heads in puzzlement. Two of my guns are perfect examples. Both were built by Remington, one a Model 90-T single-shot trap gun, the other a Model 3200 over-under. Their bore diameters are exactly the same, and the bottom barrel of the double has .035 inch of choke constriction, which is exactly the same as in the barrel of the single-shot. Forcing-cone length in both guns is also about the same. In other words, the barrels of those two guns are about as identical as human hands can make them, and yet when the exact same loads are fired in them, the 90-T delivers patterns as uniformly dense at 50 yards as the Model 3200 does at 40 yards. Even though I cannot explain why this is, I can say that I have spent enough time at the pattern board with both guns to know it is true.

Other things about shotguns are more easily explained and understood. We know, beyond doubt, that a large gauge has a greater effective range than a small gauge simply because it can handle heavier shot charges. When the 28-, 20- and 12-gauge shells are loaded with 3/4 ounce of the same-size shot at the same velocity and fired in barrels with the same amount of choke constriction, their effective ranges will be the same. Increase shot charge weights to maximum for the three shotshell sizes and the 12 will have more of a performance edge over the 20 than the 20 has over the 28. This is due to the greater difference in pellet count.

Maximum shot charge weight between the 28 and 20 is only 1/4 ounce, while the payload difference between the 20 and the 12 can be as much as a full ounce. Given the same choke constriction for all three gauges, their pattern diameters will measure the same. However, because the pellet density of a pattern decreases as the distance it travels increases, the 12 gauge has the edge in distance since its pattern contains a higher number of pellets. For example, the standard 12 gauge load of 1 1/8 ounces of shot contains approximately 250 No. 6 pellets compared to 195 pellets of the same size in the 7/8-ounce, 20-gauge load. If at a certain point downrange the dispersion of pellets in the two patterns is reduced to, say, 60 percent of the original charge, the 12-gauge pattern will contain 150 pellets versus about 120 for the 20 gauge. In other words, the 12-gauge pattern will travel a few yards farther downrange before the number of pellets it contains is reduced to the same as the 20-gauge pattern.

How much difference are we talking about? All other factors being equal, for each 1/8-ounce increase in shot charge weight you can expect an increased effective range of about five yards. In other words, the effective range of the 12-gauge shell loaded with 1 1/8 ounces of shot is about 10 yards greater than the 20-gauge shell loaded 7/8 ounce of shot. Unlike a rifle, which kills with a single projectile, the shotgun is dependent upon multiple pellet strikes, and we have gone beyond the practical effective range of shotgun and load when patterns become too thin to deliver a sufficient number of pellets to the target.