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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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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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Hap,

Velocity is speed as opposed to pattern density or lack of, which would be the hot spot of same pattern or not ... (Fast Shells spread more- do they?) that being the topic of this thread makes "speed" relavent as does what you ask when you ask, "What is considered a fast load" as opposed to not so fast ... Good Question by the way ... WPT ... (YAC) ...
 

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"Fast shells spread more"- do they?

Neil I have always wondered how fast the Road Runner could run.

Would you have any Data on that anywhere I bet Wiley Coyote would like to know so the next time he made an order from the A.C.M.E. company then he would know what speeds he needed for the equipment he buys!



I guess you would need to calculate for the curves in the road also !


Foggy!!!!
 

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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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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.

There's a fly in this ointment, which I believe Neil has admitted to in long ago posts. Hevishot. Shaped like sharp cornered pebbles. Should fly all over the place if the theory is correct. Patterns beautifully, so I'm told.

What's up with that?
 

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Last summer/fall Remington sold a low cost game load in 12 Ga. 7/8 oz 7 1/2 shot at a high velocity near 1400 FPS.

I tried to buy more of these loads this year but Remington just sends me a list of this years shells that does not include 7/8 oz 12 ga loads.


My non sientific tests were simply to shoot them at various yardages. my guestimate IS that they are as good as the regular trap low cost one oz loads and lower recoil was a benefit.


Skeet records are said to indicate that the 20 ga 7/8 oz load costs the shooter one target per 100 over shooting 12 ga 1 1/8 oz loads.

Before plastic wads some of the pellets rubbing the side of the barrel were half flattened, they left the effective area of the pattern quickly so that one could surmise that in 12 Ga a fiber wad behind 1 1/8 oz. of shot probably delivered only about 7/8 oz of shot to the effective pattern area at target range.

There must many gun magazine articles about this from a half century ago.

Hevi shot is not a flattened sphere but an erratic form, so instead of sailing off away form its initial direction it may develop rotation and spin along close to the initial direction.

This would not be tedious to check out.

Lorenzo
 

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Hap- It is possible to measure the velocity of each individual shot in a pattern with an induction chronograph. Also, it is my understanding that the velocity marked on the box by manufacturers is not the average velocity of the shot, but the mode.
Pat Ireland
 

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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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Discussion Starter · #32 ·


Pat, reading the Ansi/Saami manual, I get an entirely different take on the relationship between shell speed and "what's printed on the box."

First, mode is out the question. It's got to be mean. Second, according to the voluntary standards, all a test batch has to do is produce an average (mean) within 90 fps of what is intended. So a factory tried to make 1200 and get something close enough for their own standards - I'm sure it's less than 90 but it's bigger than anyone posting here seems to realize. That's what goes in the box. You can't standardize a chronograph with factory shells; they vary too much.

The industry standard is a 30-inch test barrel, full choke. They are all the same within anyone's ability to measure them and yet they will produce different speeds. If you visit Federal, you will see a stack of barrels and a number painted in yellow how much to correct the reading by - it'll be -15, +20, generally in that range.

My barrel is cylinder bore, that raises the speed-reading I get by about 20 FPS. This is the opposite effect from what you get with a light-operated chronograph, where a full choke reads faster. So the number I provide (1230 for example) is faster than "factory" but closer to what the home-user will get.

The speeds used in this experiment are _far_ more different that you will run into with any usual factory range. Going from light to Handicap you maybe jump 100 FPS, I covered twice that.

The shot-string (pellet variation) discussion is going right by me. What's it about?

There are hot spots in patterns. They are in the center. That's about all I can say about them which can be experimentally supported, and I'm sure Andrew will agree. The other use of the term "hot spot" may be some congregation of pellets here or there; they mean nothing since they won't be there the next shot.

More later,

Neil
 

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Fast shells

Stan4,

your explanation of why Hevishot does not scatter from irregular shaped pellets makes sense to me. If I understand you, you posit that the funny shapes only count at low speeds.

But Neil's data indicates that at high speeds, lead pellets disperse more than they do at low speeds, presumably because they are not perfectly spherical due to deformation from recoil. I must be missing something.
 

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Neil compares a fast speeds with a 10 persent difference.

This would not compare fast to slow in aircraft, fast at 1200 fps is supersonic.

This would not compare fast to slow in aircraft, fast at 1100 fps is still supersonic.

Years ago a study reported the lead loads for Geese in 10 gauge showed much better density at 1000 fps than at 1200 fps, that is twice the difference Neil used, but who is going to shoot 1000 fps loads at trap.

Huge amounts of effort are spent in refining aircraft form design, very little in locomotive design.

A teardrop pellet would have little drag, a cube high drag at high speeds there should be a significnt difference in shotshells.

Comparing no 8 pellets to an aircraft leads to scale problems which are addressed in wind tunnel work, this area could use more discussion.

ASIDE:I am finding that by continually clicking on "reload I can get on this site sometimes when it says "Service Unavailable" This kind of info is what
http://sports.groups.yahoo.com/group/TSdotCom/ was set up for.

I conclude that Neils report is valuable in showing that some pellets move out of the 10 inch core into the 20 inch circle but that the core is still sufficiently populated to take advantage of the difference in velocity.

Regards Lorenzo
 

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Neil compares a fast speeds with a 10 persent difference.

This would not compare fast to slow in aircraft, fast at 1200 fps is supersonic.

This would not compare fast to slow in aircraft, fast at 1100 fps is still supersonic.

Years ago a study reported the lead loads for Geese in 10 gauge showed much better density at 1000 fps than at 1200 fps, that is twice the difference Neil used, but who is going to shoot 1000 fps loads at trap.

Huge amounts of effort are spent in refining aircraft form design, very little in locomotive design.

A teardrop pellet would have little drag, a cube high drag at high speeds there should be a significnt difference in shotshells.

Comparing no 8 pellets to an aircraft leads to scale problems which are addressed in wind tunnel work, this area could use more discussion.

ASIDE:I am finding that by continually clicking on "reload I can get on this site sometimes when it says "Service Unavailable" This kind of info is what
http://sports.groups.yahoo.com/group/TSdotCom/ was set up for.

I conclude that Neils report is valuable in showing that some pellets move out of the 10 inch core into the 20 inch circle but that the core is still sufficiently populated to take advantage of the difference in velocity.

Regards Lorenzo
 

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Discussion Starter · #36 ·


Lorenzo, your test of 1000 and 1200 is not twice what I tested, it's the same as I tested. And I found greater density at 1030 than either 1130 or 1230, just as you did with 1000 vs. 1200.

The interesting thing to me was what so few have noticed. There's no difference between 1130 and 1230. None. Everyone is talking about speed. With these 2 - equivalent to light and handicap, speed has made no difference.

Neil
 

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1130fps shells and 1230fps shells have one thing in common. Before they reach the target they lose velocity and pass through the speed of sound, encountering turbulence on the way which disrupts the pattern. HMB
 

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I tend to agree with HMB. I too think the transition between sonic and subsonic speed is a significant factor. I do know long range (600 + yds) target shooters try to keep their bullets from slowing thru the transonic turbulence. Jim
 

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Neil- The published velocity on a box of factory shells is derived by measuring the mode of the velocity (the center of the shot cloud) of several individual shells and then deriving the mean (average) of these individual modes. Statistically, this is an error. Using a light chronograph, it is only possible to measure the fastest shot in the shot cloud (extreme upper limit). Calculating the mean velocity of 10 different shells by only measuring the fastest shot in each shell provides us with a mean that means nothing.

When you compared the patterns from shells with a stated average velocity of 1030,1130 and 1230 ft/sec, you only measured the single very fastest shot in each fired shell. This can not be used to calculate a true mean velocity. It is only the mean velocity of the upper limit of speed in each shot cloud.

I do not believe this statistical error would alter your conclusions, but I contend that your information would be more accurate if you stated the assumption that the velocity of the shot cloud (mode) would be reflected by the upper limit of velocity measured in each shot.

Pat Ireland
 
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