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Internal Geometry of Choke Tubes

Advice for the Shooter

It's what's inside that counts. A few years ago, I was asked to write an article about the differences in shotshells, in particular shotshells used for turkey hunting. I elected to entitle that article, "It's not the Shot, It's the Shell". That article, first published by "Turkey & Turkey Hunting", is still available on this web site.

When it comes to choke tubes, it's not really about the exit diameter (many times incorrectly referred to as constriction) but rather about the internal geometry.

Many choke tube manufacturers are justifiably reluctant to discuss the internal geometry of their chokes. Therefore, some shooters do not have an understanding of this topic or understand its importance to patterning a shotgun.

The emergence of "screw-in" extended chokes began with the introduction of the "Win-Choke" in the late 1960's. It was not immediately well received but Winchester stayed with the concept, refined it and it was adopted by other manufacturers as time went on. Those early chokes were pretty simple and in reality, not much thought was given to the "internals".

The folks at Briley developed their "straight-rifled" turkey choke after considering the effect that the internal geometry had on plastic wads and in turn, the effect that wad had on patterns. By reducing or eliminating the spin of a wad, the shot cup could hold the shot charge longer and would positively influence it. The resulting pattern improved.

The Hastings company recognized the importance of internal geometry and introduced their Wadlock barrels and chokes. The idea was the same as Briley's, stabilize the wad and positively influence the pattern.

Choke tube manufacturers began extending the chokes used for all types of hunting and shooting sports. With longer chokes, they could do more internally to influence the shot string and pattern than with the early short chokes. By changing the conical section, the parallel section and/or the relationships, they could do more to influence the pattern than by simply changing the exit diameter.

It was soon learned by some choke tube manufacturers that they could tweak the internals, leave the exit diameter the same and achieve different results.

This learning curve really advanced with the creation of "heavier-than-lead" loads. The inherently better patterning characteristics of those pellets, combined with some innovative shotshells, supported a creative frenzy.

Turkey choke manufacturers in particular, due in large part to the publicity afforded by contests such as the "Still Target Shooting World Championship" created by the National Wild Turkey Federation, really began to gear up and produce some innovative products.

Some of the early products produced by Comp N Choke and Kick's, with excellent internal designs, won World Championships, set records and really brought positive attention to those products. Each of those chokes has its own distinctive internal and external features that contribute to their success.

Choke tube manufacturers employ internal items such as wad-stoppers, porting of all shapes and sizes, lugs, lines, grooves and any of a number of other devices to achieve what they believe to be the perfect pattern.

One challenge that choke tube manufacturers face is the constantly evolving and changing nature of the shotshell. The internal geometry of a given choke tube may be designed to work exceptionally well with a particular shotshell or group of shotshells from a manufacturer. When the manufacturer changes that formula, the choke may not work as well and the manufacturer may have to go back to the drawing board to tweak or perhaps even entirely change his design.

The old adage about beauty being only skin deep applies here. The external appearance of a choke tube has little influence on its performance. Much of what is seen on the outside may be influenced by market studies or current trends. With choke tubes as with much else in life, it's really what's inside that counts.


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