Some interesting observations concerning pellet head sizes.

[nced]

Interesting about the posted fine accuracy folks are getting with H&N FTTs because they didn't work too well in my R9! The pellet fit in the leade was REALLY VARIABLE so I spent a week actually measuring the heads of 2500 H&N FTTs (4 tins marked 4.52mm and one tin marked 4.50mm).

While the pellets from the 4.50mm tin were pretty consistent, the ones from the 4.52mm tins....not so much. Matter of fact, there were some in the 4.50mm tin that were larger than some in the 4.52mm tin, and some in the 4.52mm tin that were smaller than those in the 4.50mm tin. Kinda made me wonder why they even  TRIED to sort by size. Anywhoo.....after sorting the pellets by size the separated lots did fit my R9 leade consistently and each sorted lot was even rather accurate! LOL....WAY too much hassle for me to sort out tins of FTTs so I tried the 4.52mm 8.4 grain JSB Exacts and I had a good replacement for the die lot marked and dated 7.9 grain Crosman Premiers. While the cases of CPLs I've bought for the last few years have been consistently accurate, the last two cases I bought also contained excess parting compound on the pellets which blackened my loading fingers and crudded up the R9 bore faster than I liked. The "dusty CPLs" caused me to go through the hassles of washing and drying the CPs before lubing for use. Another "issue" I've had with the hard lead CPs from "day one" was the fact that when unlubed they would foul the bore rather quickly, then it was a bear to strip out the "soldered (or so it seemed) fouling" since the pulled patches only polished the packed lead.

Here are a couple pics of the sorted H&N FTTs spoken of......
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com

Here is the method I used for measuring......
Uploaded at Snapagogo.com
The pellet was always on the same position on the Formica desk top, the pellet was always measured in the same position on the calliper jaws, only enough pressure was applied to just lift the pellet from the surface when measuring. Not real "scientific", however the sorted pellets consistently fitting the R9 leade within each lot did verify that the sorting method was at least useful.
Uploaded at Snapagogo.com


While I don't put much "faith" in the "4th decimal" using a digital caliper for the measuring, the heads of .177 cal pellets did vary .005 from smallest to largest which is well within the accuracy limits of my caliper. Matter of fact, even the more consistent 4.50mm tin of pellets had a head size variation of .002! Just for grins I pulled out 10 CPLs from the box and randomly measured the heads.....ALL  but two read exactly .177 on the digital caliper with the other two reading .1765! Again, I don't put much faith in the "4th decimal" but it did show that the CPL heads were much more dimensionally consistent!

Anywhoo......I found the accuracy of the 8.4 grain JSB exacts are the equal of the CPLs from my R9, I don't need to wash or lube them so I've used Exacts since last year!  Just for grinns I pulled a half dozen 4.52mm JSB Exacts from my pellet pouch and these are the readings I got (again, I'd take the 4th decimal with a grain (or shaker) of salt.........
.1765  .1770  .1765  .1765 .1765  .1765
Funny thing is that my current R9 is the only one of about a dozen that I've owned that shoots the Exacts as accurately as the CPL!

[Roadworthy]

Okay, I'll bite - what's a CPL?  I'm pretty sure it's Crosman Premier something starting with L.

[DavidS]

Okay, I'll bite - what's a CPL?  I'm pretty sure it's Crosman Premier something starting with L.

Crosman Premier Light, the 7.9 grain Crosman Premiers, the heavies are 10.5 grain.

[Kailua]

I had an idea of making a "V" shaped gauge that might help sorting pellet head sizes.  Need to get on it. 

[palonej]

I found the FTTs in 4.51 are the most consistent.
All 4 of my rifles love them.
4.52 don't fit consistently well, but shoot pretty good.
Never tried 4.50.

[gandalfretlaw]

In my experimentation I have found that each rifle has a favorite pellet head size. The skirt size seems mostly unimportant as it's a crush fit by design, but having the head rattle around in the bore is bad. The best shooting pellets are those that are just tight enough to engage the groves well. I have found RWS head sizes to be consistent and haven't really tested H&Ns. For most of my Gammos 4.48mm is perfect which meshes pretty well with RWS Superdomes and RWS Basic Match (green can). The Orange can RWS Hobby Match are tighter and measure around the 4.52 range and don't shoot as well in my rifle. Although I've never bought a box of Crossman pellets, the tin cans are all over the spectrum from 4.43-4.58 and have no consistency unless you sort them.

[Allen Rice]

Very interesting read, Ed.  Thanks for sharing, and for all the effort.

AR

[Rolling Thunder]

Ed interesting (and laborious!) project.

You may have a problem with significant digits, however.  The micrometer unlikely gives reproducible measurements at the ten-thousandths digit, and maybe not at thousandths either.  One way to test this would be to repeatedly measure the same pellet and record the result.  Also there is the issue of roundness. A pellet could average the nominal diameter but if out-of-round could give an off measurement.

Your pellet sort appears consistent with a statistical distribution, which you would expect from manufacturing - possibly a "Bernoulli process.  ie, manufacturing results in errors which are distributed randomly and hopefully within tolerance.  The question here (besides measurement accuracy) is what, if any, effect on shot accuracy do normal manufacturing errors have?

[grauhanen]

Ed interesting (and laborious!) project.

You may have a problem with significant digits, however.  The micrometer unlikely gives reproducible measurements at the ten-thousandths digit, and maybe not at thousandths either.  One way to test this would be to repeatedly measure the same pellet and record the result.  Also there is the issue of roundness. A pellet could average the nominal diameter but if out-of-round could give an off measurement.

Your pellet sort appears consistent with a statistical distribution, which you would expect from manufacturing - possibly a "Bernoulli process.  ie, manufacturing results in errors which are distributed randomly and hopefully within tolerance.  The question here (besides measurement accuracy) is what, if any, effect on shot accuracy do normal manufacturing errors have?

A good observation and comment.  Most tins, most of the time, will have a variety of head sizes and weights.  This is true of H&N and JSB, both pellet makers with reputations for quality, most of the time.  Short of measuring and weighing and sorting, pellet shooters have to learn to live with some degree of inconsistency.  It's hard to avoid.

[nced]

Ed interesting (and laborious!) project.

You may have a problem with significant digits, however.  The micrometer unlikely gives reproducible measurements at the ten-thousandths digit, and maybe not at thousandths either.  One way to test this would be to repeatedly measure the same pellet and record the result.  Also there is the issue of roundness. A pellet could average the nominal diameter but if out-of-round could give an off measurement.

Your pellet sort appears consistent with a statistical distribution, which you would expect from manufacturing - possibly a "Bernoulli process.  ie, manufacturing results in errors which are distributed randomly and hopefully within tolerance.  The question here (besides measurement accuracy) is what, if any, effect on shot accuracy do normal manufacturing errors have?

LOL....thought I had commented on  what, if any, effect on shot accuracy do normal manufacturing errors have? As mentioned, before the sort (be it a rough sort) the pellet fit in the leade was EXTREMELY variable, much more variable than when I shot CPLs or the JSB Exacts that I tested later! As mentioned, the individual H&N sorted lots DID fit the leade consistently depending on the lot, and the accuracy of the individual lot that measured .177 was very good. I also mentioned that it was too much of a hassle to measure each pellet regardless of the accuracy so I dropped the H&N FTTs all together.

Anywhoo.......the measuring effort was simply to sort the pellets into consistent fitting groups, not finite measurements of 4th decimal or "ovality"! Since the main purpose of the admittedly crude measuring did give consistent fitting pellets I believe that the effort was a success. As mentioned, the pellet diameter range for the FTTs was .005 from smallest to largest and the 4.52mm tins had pellets smallert than the ones in the 4.50mm tins and "visa versa", well within the resolution of my digital caliper. To date the FTTs have had the greatest size variation of any other pellet brands I've measured!

Perhaps I simply got a bad lot of 4.50s and 4.52s because I was surprised to read that the poster I was replying to actually had good accuracy with his, which is why I mentioned my experience with them!   

[Rolling Thunder]

I'm an airgun newbie.  This looks like a great forum and I don't want to ruffle any feathers (except pest feathers)!

I have a background in science and also statistical analysis of financial markets.  Don't know if this training is applicable, but I am seeing many aspects of pellet consistency, accuracy, belief systems, prejudice, that may play into how AR shooters may interpret their results.

For example, given the effects of emotions on the nervous system, it would be feasible for someone who expects a certain pellet to be more accurate to actually shoot it more accurately.  Subtle changes in hold, patience with sight picture, breathing, and trigger pull, could all be affected by a psychological overlay which improves or worsens groups.

(This also relates to love, as we all tend to overlook the flaws of those (people/things) we love.  ie, cognitive dissonance.  I will have more to say on this later if I don't get the boot)

That doesn't sound like physical science, but there is a huge body of research in finance (including Nobel prizes) that proves irrational behavioral biases are overwhelmingly present in what should be strictly logical decision making.

If one fired a tin of pellets through a machine AR - clamped barrel, regulated air pressure, temperature, etc - there could be a more quantitative analysis than "pellet X shoots well in my gun".  A fair criticism of this would be that *perhaps* some pellets are more "human-shooter" friendly, so a rigid machine AR is not necessarily representative. 

Back to the micrometer: I suspect that weight on an accurate scale (ie, one that reports accurate weights not just digits) is more precise/accurate than attempts at diameter estimation, simply because it is easier to weigh accurately than measure diameter of small pellets.  Surely the pellet manufacturers do very accurate quality assessment, but it is doubtful they would share it.

I am here to learn and hope my comments are construed as such.

[Pappy]

Kim .... great post, with many points made as to why we see such diversity in answers.  I am a proponent of what you explained about emotions entering the equation, and the facts about confidence and the effects it may cause.  I love this site, and the members, but I have been arguing that you can not get a finite answer to your question.  Twenty replies, 20 different answers, your post explains a lot of reasons why.
You did mention that weighing the pellets, on a reliable scale, might reveal more accurate results.  That is correct for weight of the pellet, or consistent weight of the tin of pellets.  That is important also, for accuracy, and there are many posts where members have weighed many tins of pellets with interesting results.  Ed's testing was specifically identifying the variance of head sizes compared to what was marked on the tin, and how they fit in the breech of his AG.  Every rifle reacts differently to head size of the pellet.  My TX shoots  4.50, 4.51, 4.52, and 4.53 head sizes with groupings that are relatively consistent, but the psychology kicks in with the H&N 8.64gr 4.52 head, I like the "feel" of the fit in the breech as I load it, which instills confidence, which gives me better results.
Ed ..... thanks for your efforts with the testing.

Pappy

[nervoustrigger]

Hi Kim,

Firstly, welcome to GTA!  This is indeed a great place to discuss airguns and related technology, engineering, testing, and development.  I think I can speak for us all that we are very much glad to have you here, and by the way you framed your questions and comments, I think you'll fit right in and hopefully contribute to expanding the enjoyment of the sport with your analytical mind.

What I know of psychology and emotions and how it plays into decision making will fit neatly into a thimble, but I find such things fascinating.  Much like how we are quite willing to accept dangers we (think we) understand well, but abhor dangers we don't understand...even when the understood dangers are much more statistically risky.  Like driving a car versus flying in an airplane.  Or keeping with the subject of transportation, driving a vehicle powered with an explosive flammable liquid versus driving a vehicle powered by an array of volatile lithium cells.

To the subject matter of this thread:  yes, taken in isolation, if I sort a tin of pellets by head size and subsequently test and get smaller groups with the sorted pellets versus the unsorted ones, and then I conclude that "correlation equals causation"...well, that is not terribly meaningful.  As you said, an expectation that the sorted pellets would yield higher precision may affect the outcome.  Maybe I tried harder with the sorted pellets because they should do better.

However the relationship between bore and projectile dimension has been tested and studied over and over throughout the years, sometimes with considerable scientific rigor (and often not), so eventually it has to be accepted as fact.   

I don't presume you were asserting otherwise.  Perhaps you were speaking of a more contentious subject like using lubrication on pellets or flaring skirts, or how often you should clean a pellet rifle's barrel, and whether to use Goo Gone or some other chemical, and if using weed whacker string will destroy your crown, or some other such subject that we airgunners obsess over because we want to wring out the very best from our rifles.  You won't have any trouble finding those debates here, that's for sure, so hang out a while and enjoy the ride!

[nervoustrigger]

Oh, and by the way, I'm a little concerned that everyone keeps calling Ed's calipers a micrometer.

[nced]

I'm an airgun newbie.  This looks like a great forum and I don't want to ruffle any feathers (except pest feathers)!

I have a background in science and also statistical analysis of financial markets.  Don't know if this training is applicable, but I am seeing many aspects of pellet consistency, accuracy, belief systems, prejudice, that may play into how AR shooters may interpret their results.

For example, given the effects of emotions on the nervous system, it would be feasible for someone who expects a certain pellet to be more accurate to actually shoot it more accurately.  Subtle changes in hold, patience with sight picture, breathing, and trigger pull, could all be affected by a psychological overlay which improves or worsens groups.

(This also relates to love, as we all tend to overlook the flaws of those (people/things) we love.  ie, cognitive dissonance.  I will have more to say on this later if I don't get the boot)

That doesn't sound like physical science, but there is a huge body of research in finance (including Nobel prizes) that proves irrational behavioral biases are overwhelmingly present in what should be strictly logical decision making.

If one fired a tin of pellets through a machine AR - clamped barrel, regulated air pressure, temperature, etc - there could be a more quantitative analysis than "pellet X shoots well in my gun".  A fair criticism of this would be that *perhaps* some pellets are more "human-shooter" friendly, so a rigid machine AR is not necessarily representative. 

Back to the micrometer: I suspect that weight on an accurate scale (ie, one that reports accurate weights not just digits) is more precise/accurate than attempts at diameter estimation, simply because it is easier to weigh accurately than measure diameter of small pellets.  Surely the pellet manufacturers do very accurate quality assessment, but it is doubtful they would share it.

I am here to learn and hope my comments are construed as such.

No harm/no foul for sure! I guess the only thing I care about is the poi of the pellet! If a crappy sized pellet of dubious weight will group well for me at 50 yards then I really could care less about the "minutia". Weighing pellets....been there/done that and at my skill level shooting from a bucket resting the gun on cross sticks, pellet weighing/sizing simply isn't worth the hassle!

There are folks that prefer weighing their pellets (I do have a digital scale that's accurate to .001 grain), also, there are folks that actually roll their pellets on a smooth surface to quantify the consistence of head diameter to skirt diameter, and there are folks I know that do indeed actually measure the heads of their pellets and it's all part of the "airgun fun".  LOL......for me, "fair to middlin" pellet geometry is adequate.......so if I can detect the enlarging of group sizes due to inconsistent pellet head size, then the deviation is so great that "air gaging" the pellet diameter isn't necessary! 

Peace my friend!.........The forums is a place to share ideas, even if contradictory, since almost all of us can benefit from varied input. Hummmm......I do have to mention though that there are a couple "airgun gurus" on other forums, one who boldly claims he only visits the forums for entertainment since there isn't anything he can learn from reading the posts of others! LOL....I for sure AIN'T one of them there airgun gurus .......and I do appreciate the input of others!

If I say something goofy or there is some disagreement.......lets have a dialogue, perhaps I'll change my mind and agree! 

[Rolling Thunder]

Thanks Ed and all for the welcome!  I hope to learn and possibly contribute too.

We should be able to delineate between physical and emotional POI.  Surely this has been analyzed very thoroughly by our military.

In any case it's fun to be a nerd and redneck at the same time, especially if the groups shrink!

[AudiS4]

Well by taking my digital caliper, and measuring ten pellets, ten times each, by simply turning the pellet a little everytime, I got 76 different measurements.

Have to say, that a digital caliper, isn´t a good tool to use for this job.

[DavidS]

@kim:

Good points.  And when I have found poor pellets I have used a 100% repeatable clamp to verify.    A set of 2 rigid circular clamps, measured to fit the barrel snug and made of case hardened steel.     While I am sure that state of mind does play a role as you mention, I find that the very inaccurate pellets in a given Rifle are just bad with the rifle clamped for perfectly repeatable aim.

I do thank you for that good point of view.

[nced]

There

Well by taking my digital caliper, and measuring ten pellets, ten times each, by simply turning the pellet a little everytime, I got 76 different measurements.

Have to say, that a digital caliper, isn´t a good tool to use for this job.

There is indeed a "technique" since lead is "compressible" and pellets indeed aren't PERFECTLY round, however I haven't found that pellet HEADS (not skirts) to be out of round so much that a good (if not perfect) representation of the size can be useful for presorting pellets for a more consistent fit in the leade. The "secret" is to only measure the heads of the pellet and use only enough "jaw pressure" to barely lift the fpellet from the surface. Here are a couple pic of the measuring method I used......
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com
Notice that the caliper if flat on the desk top so only the head of the pellet is clamped and also notice that the pellet is always measured at the same point in the "jaws".

Using this method with care I can indeed verify sorting adequate for elimination excessively large or small headed pellets. The point of all this isn't to make sure that every pellet is EXACTLY .1770 (or whatever)....only that the pellets with heads a thou over/under were detected and separated into different batches. A better method of "batching" pellet heads by size using a caliper is to preset the jaws to whatever size and use it as a "go/no go gage". If the pellet drops through easily or doesn't drop through the jaws it's separated into another pile for another test with the caliper jaws set at another .0005 increment. I know that the pellets WON'T be exactly .1765 diameter using even the best digital caliper, but that's not the point since the only purpose was to sort into relatively even sizes! I used the "go/no go" method a bit, however while my normal process was tedious....the "go/no go" method was UBER TEDIOUS.

Bottom line....while the head size variation I got was about .001 using my "squeeze/lift" method of sorting when measuring either CPLs or JSB Exacts......with the H&N FTTs I measured a whopping .005
variation! Wityh a .177 cal pellet, even a .001 pellet size variation at the leade can be noticed by "feel of push", and a .002 variation in a .177 cal pellet is the difference in feel between a good fit and "too loose/too tight" which MAY affect pellet accuracy at longer ranges with some guns!

[StevenG]

Well by taking my digital caliper, and measuring ten pellets, ten times each, by simply turning the pellet a little everytime, I got 76 different measurements.

Have to say, that a digital caliper, isn´t a good tool to use for this job.

Is it not also possible that your pellets are not perfectly round? I highly doubt any pellets in mass production are going to be perfectly round more often than not.

I think to make that determination about your caliper, you need to not turn them, in fact you need a way to insure you are measuring the exact thing over and over again. Ideally of a material hard enough to not deform during measuring. I am certain that with some of the softer pellets and a bit of elbow grease I could deform them during measuring.