Pellet Rolling ~~ Part 2

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..

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.

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.

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.

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?

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.

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.