Rifle Brass Sorting Experiment - Part One

[billslatteryjr]

Back when the Acculab Vic 123 came out I started weighing all kinds of things. After weight sorting a fresh lot of Lapua 6BR. I took to plugging them with primers that weighed the same and spent many hours filling them so as to get a good internal volume reading. What I found was that while there was no direct correlation between weight and volume. There was a strong correlation between the weight outliers and the volume outliers. So while I no longer spend all the time sorting by volume, I do sort by weight and make sure to mark all cases that do not fall into at the very least main 1% , approx 1.2gn , of the lot for non-comp use.

Eric, you may also be interested in experimenting by sorting by head thickness also. Easier to do than wall thickness. I had Chad from McCauslin Rifles make me up a couple tools back then to measure head thickness, figuring it's a good indicator also of wall thickness and how combustion and pressure build inside the case and recently got done sorting a couple boxes of Lapua brass. 100 of the fatter heads, about 20 of which are marked as sighters because of weight or head thickness, went to djsbrass to form into dashers for a 30Dasher project. The other 100, of which 21 are marked for sighters, the thinner will be turned into 30BRs. Like with weight and volume I found no real direct correlation between weight and head thickness. But when there's .007” not .07mm difference between the thick and thin heads there must also be a fairly direct correlation to differences in wall thickness and head thickness of close to the same weight cases?

You want to clamp everything down tight and even then there's a feel to it. Brass flash holes should be deburred first. Outside, I now use the Sinclair BR PPC since the newer blue box hole is bigger than the old gold box holes were. No longer like the 6BR Guide still has it, and inside with something that won't expand the hole. Think it's a Possum Hollow? The flat on the measuring tool needs to be just that, flat and larger than the primer pocket but small enough to enter the case. Not like the tapered end on a Wilson neck die de-primming mandrel. I know that the case's inside head isn't perfectly flat or even necessarily uniform. But I think the tools give a very good indication of thickness. Be interested in any ideas on how to measure it better, like a time consuming thin spindled 2" mic or thick spindled depth mic. But these give me some piece of mind.

 

[dmoran]

I've been stating here for years and providing plenty of solid supporting evidence that that there is a strong correlation between case volume and case weight. Many have been skeptical, to say the least, but that doesn't change the fact that the relationship exists.

Your concluding statement, "Sorting by case weight will not guarantee consistent case volumes" is not accurate. Sorting cases by weight can absolutely generate more consistent case volumes, although not always on a [single] case-by-case basis, due to the presence of outliers. For example, sorting cases into light, medium, and heavy weight groups will almost invariably reduce the total weight AND volume spreads within each group, and it will also reduce the the SDs for weight and volume. This is not debatable, it is a fact. Sorting cases by weight leads to more uniform internal volume than doing nothing at all. One can always point to a few individual outliers and claim that isn't so, but statistical analysis of case weight/volume sorting groups will readily demonstrate that it is true.

BTW - Thanks for tackling a subject that IMO doesn't get due recognition here. I enjoyed reading your write-up.

Being that not long ago you stated here on the forum that your own experience is from 223 & 308 exclusively and almost strictly with Lapua brass, would greatly limit what you deem as fact, to a very small array of all the cartridges, calibers, and brands of brass.

Like you, I to have seen strong correlation to weight/capacity with some brands of brass in specific cartridges, but have also seen poor correlation in others. And why I find falsification in such generalized deemed facts that you repeatedly claim.

 

[JimSC]

just out of curiosity does anyone know the volume of gas produced by a grain of Varget?

 

[Straightshooter1]

just out of curiosity does anyone know the volume of gas produced by a grain of Varget?

How large a grain and under what PSI?

 

[Ammolytics]

I once got curious and did my own experiment. I measured 100 pieces of 5.56 lake city brass after sizing, neck turning and uniforming pockets. I then weighed each piece on an A&D scale empty and after using water/alcohol with the kit that plugs the flash hole. Below are my results. Each cell represents a case, top rows are the weight of each empty case (rounded to nearest .1) and bottom rows are the volumes of the same cases. Was this scientifcally done? no. Did it show some correlation between wieght and vloume? I think it shows that the outliers on either side definitely have more/less volume. Did it make any difference on target after sorting out the cases to keep from 91.5 to 92.6 and use the rest as siters? That remains to be seen, my shooting isnt good enough to tell the difference, yet.

View attachment 1150411

Thanks for sharing your data! The first thing that stands out is that you measured to 0.1 instead of 0.01. I haven't referenced QuickLOAD for .223 Rem to see what difference case volume might with that cartridge, but it may be a good place to start to determine what level of precision is necessary for your use-case.

Admittedly, high-power/service rifle/sling is the one discipline I compete in but don't dig as deep into on load development. I use the same load that the top shooters I know recommend and focus more on my marksmanship.

 

[Ammolytics]

A couple of things to consider is the precision of the measuring devices used. These uncertainties build up so that you can lose precision pretty rapidly. In the case of weighing a case on a scale with resolution (display) of .02 grain you have an uncertainty of at least .01 grains. A reading of 29.00 grains might be anywhere between 28.99 and 29.01, perhaps more. Generally speaking, if I can resolve only .02 grains I’d tend to drop the 4th digit as less than significant. Or at least go to the nearest .05.

This is the crux of uncertainty.

now couple that with human interface and visual resolution, the uncertainties begin to add up. Things like, how much meniscus is present? Did a micro drop spill? Is the wind affecting the scale reading? Has it drifted, electronically?

So the measuring method and the inherent uncertainties have to be accounted.

It's true! There is always a margin of error when measuring and it helps to know what that is. Personally, I follow GLP to the best of my ability and measure more than once whenever possible.

 

[Ammolytics]

Back when the Acculab Vic 123 came out I started weighing all kinds of things. After weight sorting a fresh lot of Lapua 6BR. I took to plugging them with primers that weighed the same and spent many hours filling them so as to get a good internal volume reading. What I found was that while there was no direct correlation between weight and volume. There was a strong correlation between the weight outliers and the volume outliers. So while I no longer spend all the time sorting by volume, I do sort by weight and make sure to mark all cases that do not fall into at the very least main 1% , approx 1.2gn , of the lot for non-comp use.

Eric, you may also be interested in experimenting by sorting by head thickness also. Easier to do than wall thickness. I had Chad from McCauslin Rifles make me up a couple tools back then to measure head thickness, figuring it's a good indicator also of wall thickness and how combustion and pressure build inside the case and recently got done sorting a couple boxes of Lapua brass. 100 of the fatter heads, about 20 of which are marked as sighters because of weight or head thickness, went to djsbrass to form into dashers for a 30Dasher project. The other 100, of which 21 are marked for sighters, the thinner will be turned into 30BRs. Like with weight and volume I found no real direct correlation between weight and head thickness. But when there's .007” not .07mm difference between the thick and thin heads there must also be a fairly direct correlation to differences in wall thickness and head thickness of close to the same weight cases?

You want to clamp everything down tight and even then there's a feel to it. Brass flash holes should be deburred first. Outside, I now use the Sinclair BR PPC since the newer blue box hole is bigger than the old gold box holes were. No longer like the 6BR Guide still has it, and inside with something that won't expand the hole. Think it's a Possum Hollow? The flat on the measuring tool needs to be just that, flat and larger than the primer pocket but small enough to enter the case. Not like the tapered end on a Wilson neck die de-primming mandrel. I know that the case's inside head isn't perfectly flat or even necessarily uniform. But I think the tools give a very good indication of thickness. Be interested in any ideas on how to measure it better, like a time consuming thin spindled 2" mic or thick spindled depth mic. But these give me some piece of mind.
View attachment 1150559
View attachment 1150560

This is awesome, thanks for sharing! I did start to measure case heads thickness -- which I thinkI briefly mentioned in the article. I didn't show data for it because it seemed like a different rabbit hole and I only started measuring after the 3X firing. I'll be more consistent about it for the second experiment.

I have a hunch that there may be something to it, but I need to dig into it.

I didn't know there was a special tool, but I've found that the gage pins I have work quite well with my digital calipers!

 

[rammac]

I've always felt that directly measuring volume is far more useful then weighing, while weighing is easier it's definitely not accurate, several posters showed data that proves that. I do agree that if you don't want to actually check volumes then weighing is better than doing nothing but only as a coarse adjustment to the extremes with the caveat that you may or may not be improving the case volume consistency as precisely as you might assume. Basically grouping your case weights to anything less than plus or minus 5 grains from the mean would be a total waste of time.

Recently I found a paper written about determining what case features were of primary concern for reducing your group sizes on the target. The study, ("Statistical Methods for Determining Optimal Rifle Cartridge Dimensions", primary author Steven Matthew Anderson) written in 2002, is a scientific study and it uses statistical analysis to find what features have the greatest impact on precision. In this paper they used 400 cases and by the time they cleaned the data for errors their statistical analysis was performed on 380 cases. The conclusion was that three things have the greatest impact on cartridge precision (most experienced hand loaders came this conclusion on their own);

In descending order of effect

• Powder Charge and seating depth combined
• Primer choice

But they also studied the impact of several other case features to include case weight and case volume. The results show that case volume had more of an impact on precision than case weight, by a significant amount. But of equal importance was neck inside diameter. So the take away for me was that when tuning cartridges for greatest precision I should adjust the following features in order (top being most important);

• Powder Charge
• Seating depth
• Primer choice
• Case Volume
• Neck Tension

For my typical shooting I'll just stick with the powder charge and seating depth (I usually use Federal Match primers). If I want more precision (smaller groups) then I'll test for best case volume and finally neck tension (inside diameter).

 

[Ammolytics]

I've always felt that directly measuring volume is far more useful then weighing, while weighing is easier it's definitely not accurate, several posters showed data that proves that. I do agree that if you don't want to actually check volumes then weighing is better than doing nothing but only as a course adjustment to the extremes with the caveat that you may or may not be improving the case volume consistency as precisely as you might assume. Basically grouping your case weights to anything less than plus or minus 5 grains from the mean would be a total waste of time.

Recently I found a paper written about determining what case features were of primary concern for reducing your group sizes on the target. The study, ("Statistical Methods for Determining Optimal Rifle Cartridge Dimensions", primary author Steven Matthew Anderson) written in 2002, is a scientific study and it uses statistical analysis to find what features have the greatest impact on precision. In this paper they used 400 cases and by the time they cleaned the data for errors their statistical analysis was performed on 380 cases. The conclusion was that three things have the greatest impact on cartridge precision (most experienced hand loaders came this conclusion on their own);

What an excellent resource -- thank you for sharing this!

If anyone is interested, I did some digging to find working links to some of the other papers referenced by this one:

• Statistical notes on rifle group patterns
  https://web.archive.org/web/20120207033415/http://www.bobwheeler.com/guns/GroupStat.pdf
• Vibrations of Rifle Barrels
  https://royalsocietypublishing.org/doi/10.1098/rspl.1901.0052
• Statistical Measures of Marksmanship
  https://apps.dtic.mil/docs/citations/ADA387108

 

[SLuke]

Thanks for sharing your data! The first thing that stands out is that you measured to 0.1 instead of 0.01. I haven't referenced QuickLOAD for .223 Rem to see what difference case volume might with that cartridge, but it may be a good place to start to determine what level of precision is necessary for your use-case.

Admittedly, high-power/service rifle/sling is the one discipline I compete in but don't dig as deep into on load development. I use the same load that the top shooters I know recommend and focus more on my marksmanship.

Everything was measured to .01 but it was getting a bit complicated to keep things sorted, and since this was for my curiosity more than anything else I decided to simplify the process and round to the nearest .1. Anything .x4 and below was rounded down, .x5 and up was rounded up.

 

[mikecr]

I do agree that if you don't want to actually check volumes then weighing is better than doing nothing but only as a course adjustment to the extremes with the caveat that you may or may not be improving the case volume consistency as precisely as you might assume.

I like the way you state this, and I believe it's true.

There is no reason to assume shortcut efforts are 'better than nothing', by virtue of no more than that effort. It's possible that some cases you cull by weight deviation would have actually formed to match the mean -in capacity. And then it's as possible that some of the cases you keep, because they match in weight, will depart from mean in formed capacity.
So if your only goal is to match cases by weight, then I guess you'd be successful there, but I don't understand what that would buy anybody. I personally don't care what cases weigh barring indication of obvious problem, and they don't put me over a 17lb limit..
If your goal is to match capacities, then truly, the only way you can know it is to actually measure it. Right? YOU JUST MEASURE IT

After preps and full fire forming I measure H20 capacities. That's where I cull some. Folks might take a notion that this is wasteful in efforts, but I'm telling you there is no other way to do it, and actually know what you have.
Just as ultimately you can't know a case shoots well until it does.
Consider why capacity matters; It isn't just about load density, but also about case dynamics w/resp to expansion and spring back energies. It's a shaping of your pressure curves. It's way more than we could assume or calculate or predict.
But we can measure it.

 

[dmoran]

^^^^ +1..... well said !.!.!

Myself will not cull none until they have been fired at least twice. Volumes have not settled down enough until after at least two firings - IME (and will not use them for testing until at least 2-firings either, so that they ALL get stretched, ironed, and formed from equally pressured loads).

Here is example of how case capacity can change over the first few firings:

 

[Straightshooter1]

^^^^ +1..... well said !.!.!

Myself will not cull none until they have been fired at least twice. Volumes have not settled down enough until after at least two firings - IME (and will not use them for testing until at least 2-firings either, so that they get stretched, ironed, and formed from equally pressured loads).

Here is example of how case capacity can change over the first few firings:

View attachment 1150626

Yeah, seems to support and verify what some say about having to fire a case twice to get it fully fire formed.

 

[dnellans]

Thanks for posting data on github - makes it easy to play with it and contribute versus throw stones.

As others have noted correlation between case weight is real, but not perfect.
So the next question becomes - if you weight sort, could/should/would you expect meaningful decrease your observed variance?
This is pretty easy to calculate based on your population of data.

By computing the extreme spread, SD, and 2-SD for the sub-populations of the lightest 50%, heaviest 50%, lowest volume 50%, highest volume 50% you can see how things change pretty well.
I'm going to use the quickload 3FPS per .1gr h20 capacity for this purpose, though I'm someone will complain about that too.



Clearly sorting by h20 capacity improves the 2-SD FPS spread. However sorting by weight has a much smaller impact on SD (in one case actually making it worse, because of the smaller populations).

You -could- go add 50, 500, 5000 more cases to the study and the weight sorted group may (the overlap in the populations should go down as long as there is positive correlation between weight/volume) or may not improve (the correlation may be low enough you'll still end up with outliers in the "wrong" respective group), but we will have higher confidence because the data is less skewed by one or two outliers in 25 cases.

On the other hand, we might also conclude (now, with no more work) that if you can simply -buy- lots of cases that all fall within 1 grain variance, weight sorting them further is going to give you little to no observable improvement, though it should never hurt.

However, if you're picking up hornady range brass (where I've measured variance over 12 grains in weight), sorting them into some 1 grain lots is probably a good idea because the divergence of h20 for that weight population is going to much higher despite the non-perfect correlation.

 

[JimSC]

@JimSC
Here's QL specifications to Varget (for what they may be worth to you):

View attachment 1150606

not sure what most of those are. My line of thought is that compared to the cu ft of gas that the burning powder makes a small amount of case volume would no amount to much. Certainly not as much volumetric difference as say seating a bullet .001 farther in or out

 

[mikecr]

(the correlation may be low enough you'll still end up with outliers in the "wrong" respective group), but we will have higher confidence because the data is less skewed by one or two outliers in 25 cases.

The goal here is not to assemble correlations with confidence, but to find and remove those actual outliers (that may or may not correlate).
Forget Nobel prize,, think Reloading101: It is when it measures so, and not until

 

[dnellans]

That might be your goal Mike, but not everyone’s.

If you’re trying to find outliers versus statistical improvement, by definition, you arent gonna find them unless you measure every one, via h2o!

 

[Ammolytics]

Thanks for posting data on github - makes it easy to play with it and contribute versus throw stones.

Sure thing! Thanks for taking the time to check it out to mess around with it and share your results!

 

[Bindi2]

Q to the brains trust. The case is a means to transport measured amounts of powder to the rifle for firing. If the case volume is so critical would this not show in fps on the chronograph as ES on multiple loads ( like 2) thus making it easier and quicker to sort when fire forming or club shooting to find brass for comps. The chronograph is a cold hearted tool that gives more info than just speed if you can read it. Just discard cases that fall outside your ES parameters or into like like groups. Case prep of course.

 

[mikecr]

If you’re trying to find outliers versus statistical improvement, by definition, you arent gonna find them unless you measure every one, via h2o!

Yes, it is my contention that finding capacity outliers is only possible with measuring H20 capacities for every single case. You either want to do that and do it, or you don't and don't.

I don't credit half-efforts with more than they are.
If I have to burn out a barrel to mine 50 diamonds out of 1,000 cases, it's just a barrel. I'll be burning it out anyway, and I'll spin the field barrel on after the testing & development barrel is whipped.

I'm certain most reloaders don't engage in credible efforts to match capacities. The only time I mess with it myself is where I can actually do it. That's custom guns, where I want and expect to resolve the very best from them. And so far, that's only been a few.
I'm not a reloader who would suggest that others do this. But having done it, it's difficult to watch delusions about it spreading, and not say anything.
New reloaders need to consider truths.