doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shot Distribution in Pattern

You would need to locate actual cylinder bore guns too.

Interchangeable choke guns with tubes marker 'cylinder' are not.

With all due respect to experience and past experimenters, I am skeptical of data pre-Jones. His results clearly show that "eye ball integration" of one to a few patterns is unlikely to produce a true result. In past experimenters defense, the computational tools were simply not available. Shotgun patterns are, by nature, complex and difficult to properly analyze. Jones has gifted us the tools. We all need to use them.

DDA

I would ask anyone claiming anything about shotgun patterns to "prove it" with a 10 pattern data set run through Shotgun Insights.

DDA

Looking at both cartridges next to one another it's hard to imagine that .410 of equal choke constriction would have longer killing range than even short cased 12ga gun. If one is interested in long range killing and is lucky enough to own modern 12ga I would look at HeviShot load with 7&1/2 size pellets. I believe it is made for upland hunters in mind. The English claimed patters were great longer range. They attributed that to irregular shape of pellets.

An explanation as to why these misshapen pellets pattern so well is unlikely to be forthcoming



Rumor is that Winchester Hex-shot didn't prove to be magic as was claimed.

RocketMan
You are the guy with the golden pencil. We all rely on your computations as a firm starting point.

I think some of these questions relate to the possibility that what goes on in the gun before it gets to the choke determines a degree of the tightness of the pattern.

Someone mentioned the fact that it was commonly believed by earlier generations that a short chamber increased the tightness of patterns in trap guns. I think that is largely disputed, but the owners of those guns were not easily convinced. How do you feel about that?

This is what Bro. Compton said, which I totally do not understand

p. 129 The other variable which can be altered in the test barrel to change the internal ballistics is the chamber length. In Table 3.10 the standard deviation and pellet counts at 40 yards are given for a 36g load of #4 lead shot loaded into a 2 3/4� cartridge cases which were fired through a selection of chambers lengths. The averaged results show a definite alteration to the lateral dispersion of the shot cloud when using the wrong chamber length. The tighter pattern generated by 2 1/2� chamber length may be caused by the restrictive crimp opening acting like an internal choke.

OK Bro. Don; you're on

Better than most for sure. A agree with your first and second paragraphs. Not so sure about the second but I'm not sure what differential" is in reference to - all the shot before it reaches the choke or some of the shot in the choke (the periphery vs the center)? Do you avhe a diagram of the WS-1, Tula, or Beretta skeet chokes?

Seems like folks are arguing for Venturi like effects and claiming a choke works like a de Laval nozzle. I'm not at all sure I buy that, but I see where you are coming from. However, Venturis and de Lavel nozzles are all about the speed of gases or at least fluids. And not about radial dispersion at all. In fact, in the case of the de Lavel nozzle, radial dispersion is to be avoided (so as to generate thrust). But anyway, I'm following along. I just don't see the first principles here working to create the radial spread of the patterns that, undeniably, happen.


Just as a thought experiment considering fluid dynamics (which may or may not be relevant), take your common garden hose. Cut the coupler off the end and run the water on high. What happens? You get a long, relatively solid, stream of water about the size of the inner diameter of the hose for quite a distance before it breaks up. Sort of a full-choke type of pattern, if you will.

Now, put a constriction on the end. A reducing coupling - this acts as a choke. Water comes out faster of course (Venturi), but it also spreads much wider - much more like a cylinder choke in comparison to the first example with no constriction. Clearly, speed isn't everything. In this case, the constriction has exactly the opposite effect as the shotgun choke. But the Venturi principle is preserved, of course, because physics did not go on vacation.

Finally, into that reducing coupling, screw a 28" straight walled tube that is, let's say, 3/4 the diameter of the original hose. Turn the water back on. Now you get a solid stream like the first example, but it is going faster and further. Again, it looks like a full choke but it is, in fact, a cylinder choke, now on a smaller bore barrel.

So these three experiments seem to work exactly opposite of what happens in a shotgun choke. We have all done the hose experiment just fixing up the gardening equipment every spring. And we all have shotguns that we have patterned with different chokes. Clearly, different things happen in each. I am not so sure I trust fluid dynamics to tell me much of anything about chokes in guns. I trust it pretty well in garden hoses.

Drew, the experimental data is simply being misinterpreted on the short chamber comment. He's putting forth one theory, which cannot be correct because of the constant acceleration in the bore.

We're talking hundreds of G's here. No pellets are going to fly ahead of the end of the shot stack while in the first part of the bore. The shot column does transition from cartridge diameter to bore diameter, but it enters the choke section as a cylinder.

The most likely answer to his observed increase in pattern density, and indeed the only possible one, is that the shell mouth interference distorted the spherical shape of the rather large (#4) pellets less than the control load in a standard length chamber.

The odd shape pellets that pattern so tightly demonstrate the predominance of aerodynamic effects on shot dispersal. Those pellets quickly stabilize in flight with the projections acting as fletching on an arrow. They don't tumble constantly like the scrubbed lead pellets do that have flat sides.

Brent, as I've tried to explain it's aerodynamic forces that spread a shot cloud. The speed differential I refer to is pellet to pellet speed difference. All the shot is not accelerated to the same velocity by the choke. The leading pellets are going faster, and retain that differential for a good distance as evidenced by the continuing lengthening of the shot stream as shown in the photos. Even with the increased drag on the leading pellets and the following ones flying in their 'draft' it takes quite a bit of travel for the dispersal to equal what a cylinder choke shot cloud looks like at a shorter range.

Profiles of common skeet chokes are available on the interweb.

Just asking. If choke causes elongated stringing of the shot column in flight, thus a higher velocity for the pellets on the leading edge. Assuming spheres in good condition, why doesn't trailing shot in the column close in on the lead shot due to encountering less air resistance. And second, due to not having rotational stability of rifling, why doesn't the turbulence left by the lead shot not cause the trailing shot, in good spherical condition, to 'knuckle ball' out of the column by likely random lateral forces?