Pellet Rolling ~~ Part 2

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PART ONE

PART TWO

PART THREE

PART FOUR

PART FIVE

I have rerun the test I did out of doors last week. Which can be found here. I've done it indoors. As I mentioned these are H&N Baracudas at about 688 fps.from an HW-98 in .20 cal mounting an SWFA 10x42.

This time shot 30 shots per target and did not remove any fliers. I was indoors and there was no weather to contend with. The distance this time was 25 yards vice 25 meters.

I rolled a few hundred pellets on a Yrrah style roller I made. The catch box had 7 cells in it. Nearly all the pellets fell into the cells numbered #1, #2, and #3. The center cell was #1. The cell "above" it, that is the one on the high side of it was marked #2 and the cell below it was marked #3.

A very few pellets fell into the cells higher (4 and 6) and lower (5 and 7) but there were not enough to collect 30 samples in any cell other than #1, #2, and #3.

I shot groups for the three cells (1,2,3) and control groups "from the tin". I also shot a set of groups with the rifle's favorite pellet to establish a provable limit of my ability with the rifle under those conditions. This proves the test platform is sufficiently accurate to measure any difference which appears in the data.

I have included each target here and the aggregate group from "On Target" for each target IN THE ORDER in which they were shot.


CELL #3 (Rolled further than center)

3.1627505706.jpg


Cell3.1627506516.jpg



CELL #2 (Rolled short of center)

2.1627506632.jpg


Cell2.1627506649.jpg



Cell #1 (center cell)

1.1627506695.jpg


Cell1.1627506725.jpg



CONTROL GROUPS

FT.1627506764.jpg


FT-control.1627506784.jpg



No doubt someone will say, "Why didn't you use a PCP? ... they are more accurate." Some people can't shoot springers. Some can. To that end I have shot one additional target which shows the level of accuracy with which the rifle and shooter were performing on the other targets. In other words THIS TARGET is here because it proves the accuracy of which the system (meaning shooter, rifle, and platform) are capable is more than sufficient to measure a difference in the test pellet. This is the pellet the gun prefers ... This proves we have enough accuracy to measure a difference.

FTT.1627506837.jpg


best-for-c.1627506855.jpg


... Not finished ...

Here is the raw data:

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View attachment 1.1627595032.csv

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View attachment 2.1627595032.csv

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View attachment 3.1627595032.csv

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View attachment FT.1627595032.csv

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View attachment FTT.1627595033.csv
 
With a springer?

Don't get me wrong, I applaud your time and effort. To have some definitive data that some variety of sorting (comparing the effect of head to flare diameter in this case, through "rolling") is actually worthwhile would be great. The big issue is skewing of data that arises from using a springer as your projectile launcher. Springer's are extremely difficult to isolate shooter induced changes to impact points from inherent changes in impact points from the gun, or from the pellets, or any variation thereof. 

Impressive effort, but the fact that it was obtained with a springer needs to be taken into account b/c the data is effectively skewed as a result. 
 
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I did not put conclusions in with the data. I left that for the reader. Some will say, inconclusive. Some will say, obviously there is no benefit. Some will say, clearly rolling them helps. Some will say the test bed was not sensitive enough.

I will not conclude anything. I will direct you to the 95% circular error probable numbers at the bottom of the aggregate groups. They are:



The CEP for the "preferred pellet" which establishes we have sufficient accuracy in our test bed is 9.552 mm, about half the diameter of a dime. That's PCP country for most shooters. The average of all 4 test groups is 14.153 mm, still smaller than a dime. Clearly the test bed is more than accurate enough to measure the difference..
 
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have you thought about weigh sorting them after rolling? could you post a picture of your Yrrah roller table?
Click to expand...


I can, sir, and I'll go out in the shop and put that up here in a few minutes. 

The argument which I have heard that seems most credible to me came from @Therealld. He suggests that rolling only measures the ratio between the head diameter and the skirt diameter. I need to think more about the trig in that problem but it is certainly possible for two different pellet geometries to fall into the same cell. To prove that I'd have to spend a little while drawing. The ratio of the head to skirt is what causes the pellet to curve as it rolls down the table. I noticed as I was shooting the pellets that some of them were tight when loaded and some were loose. A pellet with a smaller head and a correspondingly smaller skirt could roll into the same cell. It just would take more turns to cover the "ground". It is a good argument.

I wanted to test ONLY the effects of rolling. You will notice there was what LOOKED like a small improvement. I think that is because when you roll pellets you pick out the ones that roll poorly, the really bad fliers. That could as easily be done by simply looking at skirts while loading.

Regarding weight sorting: I think sorting them by head size would be the first priority. That would establish a constant against which the skirt diameter would be sorted out into groups. Then I suppose weighing them might add a little something.

I did all the rolling a couple of days ago. This has been lying in the shop getting mistreated but idea is there. That is a piece of "Luan" AKA "Door Skin" sanded to 400 grit and oiled with tung oil. Slick enough for sure but still with enough bite to make rolling positive, not slippery. Some say glass is better. I printed an edge stripe so that I could mark the starting point with a pellet and marked the edges of the board so that I could replace the catch tray in the same spot after dumping (number one filled fastest). I printed four feet so that I would always have the same tilt as long as I put it in the same place on the table. Should have been plenty good enough.

roller1.1627517860.jpg

 
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Well what I see is the preferred pellet is much better than the test pellets , don't switch.
Click to expand...


:) Ha! I picked the worst pellet I have found for the rifle as the test pellet because I wanted the largest error to start with. You know the diameter of a dime is 17.9 mm. Even the bad pellets are good enough to take hunting.

That's a ten shot group on the sighter bull of the preferred pellet target. Point of aim was the bottom of the black circle on that bull. I did not include that data in the statistics. Just shot that one for fun and to confirm zero. Needed to take back a couple clicks of right windage after I saw it.
 
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other then taking a mic to each pellet do you have a method of measure the head/skirt diameter?
Click to expand...


There are people who make tools for that. It might be worth the effort. I have not found it something I wanted to do. My best accuracy has been obtained by buying a tin of pellets and measuring the head diameters of a couple hundred pellets from the tin, enough to get a fair sample of each size. Then shooting those and ORDERING a pellets a hundredth mm bigger than the size I found best when doing all the work. I have been known to size pellets and have several sizing dies. Some folks say that doesn't work for them. It has worked for me for my .22s. Some folks push a slug through the barrel and mic it then order a hundredth bigger than that.

Caveat Emptor: I am not a competitor. I just do this for fun.
 
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With a springer?

Don't get me wrong, I applaud your time and effort. To have some definitive data that some variety of sorting (comparing the effect of head to flare diameter in this case, through "rolling") is actually worthwhile would be great. The big issue is skewing of data that arises from using a springer as your projectile launcher. Springer's are extremely difficult to isolate shooter induced changes to impact points from inherent changes in impact points from the gun, or from the pellets, or any variation thereof. 

Impressive effort, but the fact that it was obtained with a springer needs to be taken into account b/c the data is effectively skewed as a result.
Click to expand...

I agree with everything said here by Franklink (as far as springers, etc) but OP did prove that with his preferred pellet he can get controlled results. And it's hard to dispute that 9.5mm CEP at 25 yards is sufficient control in comparison with the rest of the results at 14mm CEP.

My beef is with the distance. And that's when Franklink's concerns may be considered IMHO. I do not think that 25 yards is enough to discern a measurable difference (due to rolling) using JSBs. JSBs are so uniformly made that they should be stretched out to further distances to be able to see the difference Yrrah's rolling makes. Using some lower-quality pellets that have significant variances in head and skirt sizes may lead to more conclusive results at the 25 yards distance.

Also...although at 25 yards pellet weight differences (when using pellets from most modern pellet tins) are negligible, at 50 yards and beyond significant weight differences between pellets from the same tin will lead to vertical stringing. So at longer distances weighing should be part of the test to eliminate any control issues.

Thank you for the study...it's good to see such "old school" thought-provoking experiments posted again in the "new age" of airgunners seemingly jockeying who can shoot heavier and heavier led at 1500+ fps to 500+ yards :)
 
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The test pellet was not JSBs. Test pellet was specifically selected because it is the worst performing pellet I tested in the rifle.

When testing.one aspect of a problem it is generally a bad idea to complicate the problem by adding variables. If I want to know how much impact weighing pellets has the best experiment will not also require me to roll them. This test is designed to discover how much taking pellets from the tin and rolling them impacts group size.

Also if the test bed is sensitive enough to see the difference between the preferred pellet and the test pellet. It follows it is sensitive enough to detect any statistically significant difference between the various groups sorted by rolling.

Wind drift becomes enough of an error component at longer ranges to invalidate the test results outdoors.

The test was done outside at 25 meters in part one. Which is posted in this section The results were comparable. I'd love to see someone run a hundred and fifty shots outdoors with their PCP shooting pellets at a hundred yards AND collect meaningful data. It would take five times as much data (say 500 shots) to make that exercise plausible. It just about has to be done indoors.

Fifty yards indoors with an accurate tethered PCP would likely be about ideal.

Last question... Do these 1500 fps shooters shooting 500 yards hunt squirrels in the deep woods with all that "new age" hardware?
 
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The idea of rolling pellets to sort for head size is based on the assumption that the skirt diameter is consistent. If the skirt diameter is not exactly the same….you cannot glean any useful head size information from the method.

If pellet companies can make the skirt diameter consistent, but not the head size…maybe the pellet making machine should be turned around?

Back when pellets came in tins with tape around the outside….I noticed that some of the tape was applied in a clockwise fashion and some counterclockwise. I took two tins with opposite tape application and shot an outdoor benchrest card each in poor conditions with my worst shooting barrel and gun using a broken scope. The clockwise application tape was considerable better. I will let you make your own conclusions about the test. 

Good stuff.


 
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"A mike can NOT accurately measure those diameters, it really takes a “tri-mike” to do it,"

What about a pelletgage?

Assume for the sake of argument that a 4.51 head diameter is "perfect" for YOUR barrel. The available lead engages concentrically when seated and seals fully. Introduce a 4.52 (or larger) head diameter. As many have noted, the barrel will "size" the pellet. What would that "sizing" do? Seems it would take the additional lead and squeeze it into the space available. Would that increase the contact area between pellet and barrel? Seems it would. Would that increased contact area increase friction? Seems it would. Would the larger diameter pellet weigh more? Maybe, maybe not. But it might. Could any increased friction and additional weight effect muzzle velocity? Seems it could. How would the different shape created by the "sizing" of the larger diameter pellet effect the pellet in flight in comparison to the "ideal" size pellet? 

Would the larger diameter pellet "roll" to the same spot? If head and skirt were larger by the same amount then it seems so.

Is any of this actually relevant and usable? Probably not.


 
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The idea of rolling pellets to sort for head size is based on the assumption that the skirt diameter is consistent. If the skirt diameter is not exactly the same….you cannot glean any useful head size information from the method.

If pellet companies can make the skirt diameter consistent, but not the head size…maybe the pellet making machine should be turned around?

Back when pellets came in tins with tape around the outside….I noticed that some of the tape was applied in a clockwise fashion and some counterclockwise. I took two tins with opposite tape application and shot an outdoor benchrest card each in poor conditions with my worst shooting barrel and gun using a broken scope. The clockwise application tape was considerable better. I will let you make your own conclusions about the test. 

Good stuff.

Click to expand...

That does seem to be what the numbers indicate. Maybe someone with a five thousand dollar PCP and a 180 yard outdoor range should confirm the data? Just kidding.

I really like the humor. It was quite well done. :)

Sometimes you do an experiment and discover something you did not want to discover.  That's what happened in this case. The last thing I wanted to do was tell @yrrah that I could not show his idea worked. Thanks for doing that heavy lifting for me. You told him. I did not have too. Reference the first test outdoors and the parts I have stricken, the push back I gave @therealld there, the citation I gave him here, and the conclusion to which you have come. 

You don't need an atom smasher to drive a nail. ;) I think, that's what you said.

With respect, sir.
 
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Cornpone..



Try using a thick piece of glass to roll on

the wood grain will hamper the pellet rolling. Also be careful as to how fast they roll, they'll "skid" out and skew the test. I got decent results by having the "rolling table" be raised about 3/8-5/8 inch
Click to expand...

Yes, I agree with you, the slower they roll the better result you will get. The feet on my table are 40mm on the high side and 20mm on the low side. The table is 12" wide. They roll pretty slow.

The wood was sanded slick with 400 grit paper and finished with tung oil. That was not a problem. But if you got good results with your setup maybe you should shoot the targets and show the data. I'd be happy to run the targets for you through the software I use to analyze them. I have enough confidence that I collected good data that I am going to move along to other tests. This thread was just the beginning of an effort to put to bed anecdotal information with real data. But like I said, seriously, anyone that wants to repeat the tests should easily confirm or refute the numbers I posted. Anyone who feels there is a problem with a using spring rifle to do the test should most certainly rerun the experiment and document their results. I will be more than happy to run the targets for them and provide them with the spread sheet data and aggregate targets. Matter of fact I'll upload that in links at the top post right now.
 
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