Shot String Pros And Cons

Dear Technoid

I read and re-read your comments on “shot string” and I don’t understand your comment of a 12″ effective pattern. Your comment was: “Your effective pattern width (80% chance of a two pellet hit defining the fringe) at 40 yards with maximum choke and 11/8 oz of #7.5s is only about 12″. That 30″ effective pattern hype at long yardage is just dreaming”

Could you elucidate on why the killing pattern is only 12″ wide on a six foot shotstring.

Roger

Dear Roger,

Conventional shotgun patterning is two dimensional and does not deal with the third dimension of shotstring. Conventional paper patterns mimic the straight-away shot, not the crosser. This isn’t as bad as it sounds because in the real world

1) there is just as good a chance of getting a straight-away as a crosser and

2) different shells have different shot string based on shot hardness, wad efficience, etc.

Using a two dimensional straight-away pattern as reference eliminates the infinate variables of shotstring and varying target angle. It makes comparisons easier.

Shotstring can both add to effective pattern and subtract from it. Brister’s “Shotgunning: The Art and Science” seems to be the most referenced work on shotstring, though Roger Giblin’s impact computer array in England was far more advanced. Brister made the process appear simple by getting his wife to tow a huge pattern board behind their car. Typically, the pattern taken when the board was stationary was a circle, while the pattern taken when the board was moving was laterally oblong, perhaps a bit like a football or swarm of bees.

In any case, patterns on a moving plate show a sideways elongation of pattern due to shotstring. That’s because some of the shot gets deformed, thus becoming less aerodynamically efficient. This causes some of the shot to arrive on the pattern sheet later than other, rounder shot pellets. The pellets at the front of the shot column hit the papter. The paper moves. The pellets in the middle hit the paper. The paper continues to move. Finally the rearmost pellets hit the paper. This is what causes the string. The patterns in typical stationary vs moving comparisions show equal pattern heights, but differing pattern widths.

Now here’s the point of it all: since the pellet count doesn’t change, the straight-away pattern (representing the stationary pattern test) puts the entire pellet load into a circle. The moving shot (representing the shotstring) puts the same number of pellets into the larger oblong area. This means that the pattern representing the crossing shot with shotstring is larger, but thinner. The density of a pattern (hits per square inch) governs is effectiveness.

Go back to the small size of that long distance pattern I mentioned and consider the long shot string. If (big IF), your shotload has an excess of pellets, the shotstring may indeed increase your killing pattern. This is quite common with a typical 1-1/8 oz skeet load of 651 #9 shot. Shotstring is good for skeet crossers because there are so many pellets in the load that the pattern can afford the dilution of shotstring and still benefit from a larger effective pattern. This is because it has extra pellets to squander. That’s why sophisticated skeet shooters (like the Russian team’s development of the Tula choke) go to some effort to promote shotstring. That’s something not always easy to do in an open choked gun.

But the typical payload used for longer shots doesn’t have excess pellets. It doesn’t really have enough to begin with. A 1-1/8 oz load of #7-1/2’s has 389 pellets, not the 651 of #9s. With #7-1/2s the dilution caused by a long shotstring thins out an already thin pattern. While this certainly does increase pattern size in general, it does so at the expense of effective pattern size. Bigger pattern, but thinner. That means a smaller “effective” pattern due to shotstring thinning. In these cases, an excessively long shotstring is bad. The longer the shotstring, the more the dilution. In this cases it pays to do everything you can to shorten the shotstring (high quality pellets, good wads, proper powder burning rates, barrel interior modifications). This is the direction that the old lead waterfowl loads went and why John Olin had Winchester go to harder plated “Lubaloy” shot. It was to decrease shotstring and increase effective pattern area.

There. Is that enough elucidation from your SR elucubrator? Or is it just more eluvium from your Technoidal elutriator?

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)
http://www.ShotgunReport.com