Science Chokes

Picking the right choke-and-shell combination for a given situation can be serendipitous (dumb luck—my personal savior), mythic or scientific. All three approaches work, which gives you some idea of how unimportant the right chokes and shells are compared to pointing the gun in the right place.

The ballistic decisions that the goddess Serendipity makes for us usually are the result of shooting whatever chokes your favorite gun already has in it and stoking said with whatever shells were left over from your last shoot.

Mythic selection of choke and shell might stem from recalling some fabulous shot you or a friend made with a certain combination and then attempting to duplicate it. You might also remember something you read that caught your eye. Outdoor writers are myth-makers of heroic proportions, at least in their own estimations.

And then there is science. You know that stuff. Scientists are the guys who warn us about global warming during one of the colder winters on record. Personally, I like the scientific approach to ballistics because doing all that testing keeps me out of the malls. 

Actually, figuring out the right choke/shell combination for any particular bird or clay presentation isn’t all that hard. You figure out the vital area of your target, how many pellets at what energy you want to hit that area, and then you do the math.

Here’s an example: Suppose I want to shoot plantation quail. My betters tell me that No. 8 shot is plenty for these birds. My 28-gauge quail gun uses 3/4-oz cartridges. Three-quarters of an ounce of No. 8s is 307 pellets. My best guesstimate of the vital area of a quail is nine square inches once you add in vital appendages. My goal is to get the largest killing pattern possible using the above input.

Next I turn on E.D. Lowry’s “Shotshell Ballistics for Windows” computer program. Lowry was head ballistician for Winchester for years and writes stuff you can believe. Fussing with the program shows me that I’ll need 75% to 95% (230 to 292 count) of my No. 8s inside a 30” pattern circle to optimize my pattern. I can expect a functional pattern diameter of 20” with anything in that percentage range.

If my pattern is more spread out, say 60% in a 30” circle, my pattern diameter thins out too much at the edges and the effective part actually shrinks to 12”. I define an effective pattern as one with a 95% chance of a one-pellet strike, which is the same as an 80% chance of a two-pellet hit or about a 50% chance of a three-pellet hit.

The bottom line is that when using 3/4 oz of No. 8s on a nine-square-inch target, I want a pattern that puts 75% to 95% of my pellets into a 30” circle.

All you do is figure out at what distance you want to do your shooting and see which choke gives you a 75% to 95% pattern at that distance. Nothing easier. Since most of my quail shots are in the 20- to 30-yard range, it looks as though a light Skeet and a Modified would be about right for my 28-gauge right and left barrels.

Does this analysis jibe with the way you set up your chokes? What does your real-world experience tell you?

That’s it for now. Boots off. Beer open.