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"Fast shells spread more"- do they? (Winston)

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"Fast shells spread more"- do they?

“The effect of shot speed on pattern width is known by all but properly exploited by but few. When you need just a bit more spread and don’t want to bother with changing chokes, just slipping in the next “speed group” – say substituting “heavy” for “light” – can give you just the edge you need, with the bonus of extra pellet energy at the target that changing chokes won’t accomplish.

But you’d best not try this without regard for the physics involved, as thoughtless changes can be more trouble than benefit. Here’s why: pattern development is dependent on air drag, and that drag is not a simple monotonic function of pellet speed, but rather is a function of the square of the speed. So the effect of pattern-widening is magnified at the upper reaches of pellet velocity. Here is an illustrative figure:



And it’s that huge increase in pattern-width at the right side of the graph that can lead the unthinking claysman into trouble. Trying for that last bit of pellet energy for a 60-yard crosser, he loads up with 1400 FPS and pays twice for his mistake: By the time the pattern gets out there it’s often too spread out to even clip off a “visible piece” and the recoil – which he has suffered for no benefit - will affect his shooting for the rest of the day.”

I pen that last period and lay down my quill, letting my eyes drift back appreciatively over the text. Very good – very good indeed! Beyond just repeating what every reader will agree with, I offer not just scientific causation but even surprising graphical evidence, as well as both support and warning to my readers, which about covers the bases, to my mind. OK, that “instrumental” flourish on the x-axis of the graph might be a bit over the top, but it lends such an air of erudition to the enterprise it’s just too good to pass up. If the response to this article is favorable I may be able to string this out for a couple more issues, dreaming up wad and powder effects, interactions with shot size, whatever comes to mind; you know the drill.

Time again to reflect how good I have it. An evening in my den in front of the fire, building castles in air for yet another shooting publication. My ever-more-grey-muzzled retriever curled at my feet, napping and no doubt dreaming about the day in the field I promised him next month when I will pretend to test a brace of matched Purdeys. How can you beat it?


Admit it – you were well into this before you first began to smell a rat. The first parts are so much like what you read everywhere, hear at every club, I dare say they slipped past your BS detector without raising any alarm whatever. So now backtrack and see how far you have to go to find some fact –

Back 1: the “60-yard crosser” paragraph. Well that was a giveaway, wasn’t it?

Back 2: The graph. Sure, that’s a graph of squared numbers, but is it possible? I hope you don’t think so!

Back 4: This is the support for the graph. If it’s nonsense, so is this.

Back 5, right to the start. Unfortunately, there’s hardly a word of truth in it either. In fact the first 12 words, “The effect of shot speed on pattern width is known by all” are as questionable as any of the other fibs I told.

Introduction:

I’ll bet that every reader knows that when you push shot faster the pattern “opens up.” But what happens when I now ask you “How much?” On the off chance that you have an answer to that, I keep another question in reserve: “How do you know?”

This article will cover an experiment involving shot speed and pattern width. For a limited set of data, it answers those questions which I’ll wager stumped most of you: “How much?” and “How do you know?” Based on data from 10 patterns each from shells measured at 1030, 1130, and 1230 feet per second, it will report some statistically significant differences, and some cases where the “expected” differences failed to appear.

Properly, this is the first test of patterning which should be done, since it answers the question of how well speed has to be controlled in comparing shells, chokes, powders and so on. If a difference is found is it due to the change in components or equipment, or could shot velocity be responsible for the whole finding? Conversely, if no difference if found, is it speed making a change in one direction and “canceling out” a change in the other, thus masking a real effect?

The best experiments make you re-examine your ideas, perhaps even change your mind or behavior. This experiment has led me to put some of my MEC bushings away in favor of bigger-numbered, larger-holed ones. With luck, it may change your outlook as well.

Equipment:

The critical piece of equipment making this experiment possible was the software program “Shotgun-Insight”, an application which reads digital photos of patterns and analyses them, making it possible to read enough patterns to draw reasonable conclusions from them. The rest of the equipment used: pattern paper, a digital camera with flash and tripod, PC and the rest, act only as support for the program. Kaleidagraph software produced the graphs.

Method:

A MEC 9000H was used to load once-fired STS hulls with Red Dot – 15.7 grains, 17.7 grains, or 19.7 grains. With the components used, the resulting speeds were about 1030, 1130, and 1230 feet per second, as measured by an inductive chronograph, and the 10-shot standard deviations of all were under 5, which is consistent ammo indeed. The shot is Remington magnum 8’s with a count of about 440 per load as dropped by a 1 1/8 oz. MEC bar. All shot is from the same bag.

On a warm day at Metro Gun Club in Blaine, Minnesota, patterns were produced firing a “factory bigbore” Perazzi which has produced consistent full choke patterns in other experiments. The distance used was 34 yards, in an effort to make more use of the “75% diameter” statistic offered by Shotgun Insight. Ten patterns were shot at each shot-speed.

The digital photos were intentionally overexposed by one stop and a fill-in flash was used; all the resulting JPEG’s were usable.

Results:

Here, in bare-bones form, are the results of the test.



Based on averages (mean), the patterns from the 1030 FPS loads were denser in the 0-10 inch and 10-20 inch diameter rings than the others and the 20-30 inch diameter ring was less dense. The innermost-ring differences were not statistically significant (I.E., roughly, they could reasonably attributed to chance) while the others were significant.

Look, even I see this as something of a letdown. Hours of work resulting in 12 numbers only four of which mean anything? I plan to go on with “How much?” and “How do I know?” to show what’s behind those numbers, but in the end, those are the “experimental results.”

Let’s look at the data as it comes in, that is, shot by shot.



Looking at the traces from the top down on the graph, the first, the black line and open squares, shows that the pellet count is stable, pattern-to-pattern.

The green dots, connected by a green line, are the pellet counts in the 10-to-20-inch ring. This count too is quite stable.

Going on down, we meet the red trace, the pellet count in the inner 10 inch circle, and the blue trace, the 20-to-30-inch ring. They are more variable than the others, and in addition, vary inversely, that is, when one goes up the other goes down. When there are few pellets in the center there are more on the edge and visa-versa, while the 10-20 inch ring just tracks along. No, these pellets are not jumping from the inner to the outer rings, it’s just that even when the total number of pellets in a 30-inch pattern is the same, some patterns are more spread out than others. “Spreading out” means some 1-10 drifting into the 10-20 area and, at the same time, 10-20 pellets drifting into the 20-30 area. The sector with the most pellets is the one from 10 to 20 inches, but since it is 3 times the area of the 10 inch circle, the pellet density is only about 2/3 that of the center. Once again, these patterns are “hot in the center” like all the others intended for trap shooting.

So what does a significant difference look like?



The shots have been ordered according to total pellets in 30 inches, increasing left to right. The 1030 patterns are the solid markers and lines; the 1130 are outline markers and dotted lines. We see some real differences here. The 1030 FPS 0-10 and 10-20 rings are more dense, less dense in the 20-30 inch ring. So, in fact, increasing the speed 100 fps with this slow start has widened the pattern, much as opening a choke tries, but mostly fails, to do.

And what do non-significant differences look like?



Here the traces cross and re-cross each other in random ways and are often just the same. In this case, starting from a faster baseline than the first graph, increasing shot speed by 100 FPS did not widen the pattern.

Another way of looking at this is the “75% diameter” statistic. This is a calculated rather than counted datum which predicts a circle diameter which would contain 75% of the shot.



This is the same story as told by the “rings” analysis. The 75% diameter of a 1030 FPS shell is smaller, that is, the pattern is smaller.

Just a couple more things. Could I have gotten these results by other means, specifically “by eye” or “side-by-side inspection” or fewer patterns?

No, and here’s reason 1. There’s too much overlap:



Most of the time most of the rings look about the same across all speeds. You can’t possibly tell more than a couple apart, much less several at once.

And here’s reason 2:



If I’d shot just the first 5 I’d say that 1130 FPS had a hotter center than 1230. If I’d shot just the second 5, I’d say that 1230 had a hotter center than 1130. It’s only by shooting all ten can I see that there’s really no difference between them at all. You need at least 10 patterns to avoid being misled.

Discussion:

Based on this, I’m going to speed up my first-shot-doubles shells to about 1150 FPS from the 1050 FPS range I’ve been using. They are 1-oz. anyway; why not give myself a better chance? I’m going to try Extralites at handicap. Just to see if they are denser – denser enough, that is, to help.

Is the odd effect seen here related to sub-sonic v. super-sonic? Someone here, maybe it was HMB, made a big deal of that in an earlier thread. Could he have been right? Some evening I’ll settle down by the fire with Kyra at my feet and explain it all for you.

Yours in Sport,

Neil
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At the very beginning of this article, I thought Neil had read too many reloading articles written by Rodney Reloader of "skeets" magazine. Good job Neil, well done and to the point for the velocities and distance the patterns were shot. Are we left to assume the high end numbers may be projected farther out, say, 42 yards with even higher velocity loadings while maintaining the same sort of ratio? Probably for singles shooting, an average is real close to 1145-1200 for most shooters would be a guess on my part. For long handicaps, choosen velocities may be somewhat higher as an average? If true, how would the average singles load compare, percentage wise if a higher velocity load were used from the max of 42 yards? Such as the max limit for velocity with either 1-1/8 @ 1290 or 1325 with an ounce? Thanks. Hap
 

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Harold, your right,there's no data in Neils work making such a suggestion. "There is nothing in Neil's data to suggest that a 1450 fps turkey load would be any worse than your 1150 fps load."

Are you saying that the 1150fps load of number 8s and a load of the same at 1450fps at 42 yards would also follow the same percentage path as suggested by Neils tests?

Like Andrew, I'd like to see some comparison facts between the 1150 versus 1290 at long handicap yardage such as 42 yards. Hap
 

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A lot of importance is being placed on the velocity of the leading pellets compared to the entire shot-string. With a shotgun, shot patterns, velocities and other variables are practically non-existent. How much difference between the leading pellets and the following shot is there? How important would that information be id we had the equipment to measure it exactly? Not much in my estimation. In the tests Neil completed, this is his statement to me. "Hap, I referred in the article to a "limited data set" and that's what it is." If another test was performed using the same components at the same distance with a different shotgun, would the results remain the same? Maybe, maybe not. Too many variables to make a cast in stone prediction of exacting percentages. Regardless of load, choke constriction and barrel length we choose, an average may be the best hoped for outcome. "Fast shells spread more"- do they? (Winston)
The real question here is, what's a fast load? Certainly a load of 1230 seems fast compared to one of 1030 but is it? Since we have an upper limit on velocity for regulation ATA shooting, my ideal test would compare an average load shot at singles at 34 yards to see if the upper limit loads did in fact spread more with the same size shot? I mention this test because some shooters use the same single barrel for singles and long range registered shooting with different velocities. At what velocity does a round lead sphere begin the curving effect from velocity alone? Hap
 

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Bill, it's my understanding that ammo makers use a 30 inch cylinder bored pressure gun to come up with velocity numbers for such n such load and stamp the average velocity on the box. Shooters chrono those loads from a 34 inch full choke and get a different reading, velocity wise. Is that difference due to the barrel being a full choke alone or does length play any part in that equation? Would the numbers be different if ammo makers used a 34 inch cylinder bored barrel? We've all seen high speed photos of shot exiting a barrel? Is the front part going that much faster than that at the back? Thats the part I doubted could be actually measured with any accuracy and I give that less importance, thus my comment above concerning velocity and its importance. Hap
 

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Pat thanks for the information. Having never seen a graph of an induction chrono result and differing velocities of pellets within that group, I ask this. Are the leading pellets going that much faster than the remaining shot? I understand the "squirt effect" of a full choke compared to a cylinder bore, but, shotstring lengths don't bear this out when taken with high speed photography? When we talk speed of this load or that one at xx.00, irregardless of ammo makers method of determining what's stamped on the box for a number, we use available tools for a comparison to those numbers listed. Compare too the SD numbers from Neils handloads and most factory loadings. I'm not sure what that information tells most but it tells me my handloads are more consistent than most factory shells. If that's true, wouldn't measured velocities from those handloads also be more consistent? They have to be in my opinion shell to shell.

Lorenzo, just my theory on why Heavi-shot performs as it does. Harder and heavier than lead, teardrop and other ugly shapes right themselves forward with the heavier portion forward which leads to those great patterns. Another opinion only. Hap
 

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BuckGuru wrote this as his understanding as to why pellets spread excessively in a pattern. I have to ask the question below.

"All the articles I have read about the effects on the pattern from increasing speed attribute the spreading to shot deformation. The theory is that shot gets deformed from high velocities and thus flies erratically."

Since steel shot doesn't deform as lead does, shouldn't steel pattern better due to perfect round spheres unlike flat sided round lead balls? I think if that were true, steel should act more like Hevi-shot but it certainly doesn't, so, does that mean other factors come into the equation? Weight of individual pellets and speed is directly proportional after passing a certain velocity.

ZZT above remarked about his findings with hunting loads. Neils findings of 1130 and 1230 number 8s are the same for pattern purposes. I wonder at what velocity above 1230 would we see the percentages change as seen from 1030 to 1130 and be a legal trap load? Fall is a great time to pattern our shotguns. Hap
 

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I just finished re-reading that one again Neil, thanks for the link! That thread is also very informative and good information for shooter's serious about the consistencies of their re-loads! Thanks for sharing your findings! I've improved my loading skill and have always taken pride in my home-mades. Once I find one that works well for breaking targets for me consistently, I experiment with diligence for the best flavor of the month and hardly ever change much at all.

Thinking back to reading of Arnold Reigger's winning abilities on the HOF site, most of his winning ways were shot with a 2-3/4 dr. load! There's a lesson to be learned from that and the valuable input you share with us! Thank you sir! Hap
 
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