Shotstring And Patterns

Exalted Technoid,

I am a bird hunter and sporting clays shooter who has studied your advice religiously, especially on the subjects of chokes and patterns. I have followed your advice for the most part, including purchasing and using the Choke Chooser to help select chokes at sporting clays. As a result, most of my shooting companions consider me to be hopelessly overchoked.

While browsing through a bookstore recently I picked up a book on upland and waterfowl hunting edited by David Petzal. I believe the book was published in the 1970’s. It it is a chapter on dove hunting by Bob Brister, who I read and study even more religiously than I do the Technoid (Sorry).

In this chapter, Brister mentions that Ennio Mattarelli, designer of Perazzi shotguns, had a device that swung a shotgun in concert with clay targets and measured the effectiveness of different chokes on targets thrown at different angles. Mattarelli concluded (and Brister concurred, based on his target, field and flyer experience) that significantly less choke could be used on crossing targets than straightaways.

My left brain says “no way”, reasoning that a given target profile is the same whether it is still, moving sideways, or moving directly away. (I realize that real birds present different profiles depending on direction of flight, but that was not the point of the statements, at least as I understood them.) It is true that a clay target can run into a trailing pellet due to shot stringing when it had otherwise escaped the front of the shot string due to a “hole” in the pattern. However, it seems just as likely that it could move out of the way of a trailing pellet. At any rate, given the minuscule distance a clay target moves during the .01 second or thereabouts it takes the shot string to move past it, either occurrence seems to be a pretty minor factor.

But my right brain says “Who am I to dispute the likes of Bob Brister and the designer of Perazzi shotguns?” A lot of research on shotshell ballistics has been conducted since the chapter was written, and I have never read a similar statement by anyone else. What is your opinion? Or, if you know the truth, I’d be even more interested in that!

Asotin, Washington

Dear Larry,

Didn’t Mattarelli (sp?) win the ’68 Mexico Olympics with a Perazzi? I think so. The two of them certainly ought to know what they are talking about. Ought to anyway.

The bottom line question is “Do you need less choke for crossers because of the effect of shotstring?” If you like Brister and take look at the photos in his book “Shotgunning, The Art and Science”, you’ll see clear evidence that a shotstring can dilute the pattern on a crossing shot compared to a going away shot. When Brister talked his wife into driving that trailer with the pattern paper on it, he did some interesting tests. One was taking a shot at the pattern paper when the trailer was stationary (as we do when taking standard patterns). He then compared that with a shot from the same shell/gun combo taken at the paper when it was being towed at speed. One of his tests shows a duck load of #4s printing 50% at 50 yards stationary and 36% moving at 40 mph crossing. One grex buffered load printed 88% stationary and 76% moving at 40 mph. Brister considered that pretty good quality. In other pattern tests, with higher quality ammo, Brister found little evidence of pattern degradation due to stringing. It really depended on the quality of the shell.

So, in most cases shotstring degrades the pattern to some extent on a crossing target. In a few cases it degrades it very little or not at all. In NO CASES does shotstring improve the pattern UNLESS you start off with a surfeit of pellets. Example, a 12 gauge 1-1/8 oz skeet load has around 650 little lead soldiers on its side. At 20 yards, even from a cylinder bore gun, the pattern is so dense that it is highly unlikely that a target could sneak through. There are actually more pellets than statistically needed to assure a break. So why not “invest” those extra pellets in a shotstring? That’s exactly what many skeet chokes try to do. They try to artificially elongate the shotstring so as to bring those extra pellets into play. That was the whole point of the Russian Tula choke- lengthening the shotstring for skeet shooting.

It’s exactly the opposite on longer shots. There isn’t a surfeit of pellets in that case. The big problem when the bird is farther away is to get enough pellets into the pattern to assure a break. Some pellets that go into the shotstring are removed from the effective pattern, making the center weaker than it ought to be. You want no dilution due to shotstring because you don’t have extra pellets to waste. You aren’t using masses of #9s for long shots. You are using many less #7-1/2s. In this case shotstring is bad.

So, I don’t really understand from a pure pattern point of view how Mattarelli or Brister could use a more open choke on a crosser than you do to break a going away target. I would think that you would need an even tighter choke because your pattern on a crosser is being diluted by the shotstring.

There is one factor that wasn’t mentioned that may hold the key: A straightaway has the speed to the target (perhaps 60 fps) subtracted from the speed of the pellet at the target (say 675 fps for a #7-1/2 at 40 yards started out at 1200 fps). That means that the effective striking speed of the pellet on a straightaway is 675-60 or 615 fps. On a crosser, the effective striking speed of the same pellet is the full 675 fps. That’s a difference in energy in excess of 18%. That might be why you can get away with a more open pattern on crossers than on straightaways. More pellet energy is delivered on the crosser, so you need fewer pellets. If this were the reason for Brister and Matarelli’s opinions, we would both be right. Oh, frabjous joy!

As to your friends claiming that you are overchoked when following the Choke Chooser’s advice, perhaps you are (I don’t know exactly what you are using when), but consider the following. When you center a target you ought to get smoke, or at least a very heavy break. That’s the only way you know for sure that you have optimized your pattern. Huh? Yup. Here’s how it works.

ALL patterns are denser in the center than at the edges. Has to be. Got to be since all normal patterns are Gaussian in nature and follow the immutable laws of the bell curve. If your pattern is always denser in the center, then to get an adequately dense outside fringe ring it HAS to be too hot in the center. If it’s just right in the center, by definition you have no fringe. Pretty simple. Well, it’s simple when someone really smart explains it all to me.

So, that may not be the truth, but it’s my opinion.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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