Rifle Brass Sorting Experiment - Part One

Hey everyone!

I published the first part of an ongoing experiment which explores the relationship between the weight and volume of rifle brass.

https://blog.ammolytics.com/2020-01-08/brass-sorting-part-one.html

The results were pretty interesting, and I was surprised by a few of the findings. I hope that it's high quality enough to justify the time you spend reading it, and how much time it took me to create it.

I'd love to hear your feedback and answer any questions!

 

sample size is too small
survey size is too small
no definition of shooter type(hunter/br/prs)
converting to or from grams to grains does NOT AFFECT ACCURACY NOR PRECISION.
do not stop, just doo more research BEFORE establishing a test

 

My 2 cents, this was done at 600yds fclass, 6mm, bra, vapor trails 103gr bullet, lapua brass. I would always sort brass but never was convinced. I took 5 cases that were the heaviest and 5 cases that were the lightest, all cases had 5 firings on them and had been annealed and trimmed as usual. Shot all 10 rounds, all 10 shots were in the xring with absolutely no evidence visual to me that one made a difference over the other. I will add that I always turn necks so I know tension is consistent. I have never weight sorted since. No verify scientific but good enough for me.

 

The point he's making is that a balance which offers a choice of 1mg readability or 0.02gr readability (like the FX-120i used in this case) provides more resolution by taking measurements in the gram scale then converting the results to grains. In the gram scale the resolution is 1mg, while in the grain scale the resolution is 1.296mg - nearly 30% coarser.

 

Thank You for posting the results of your test.

May I ask;
What was the case weights and weight spread of the 5 heaviest cases
and
What was the case weights and weight spread of the 5 lightest cases

I'm hoping there was at least around 5 grains difference in weight from the lot you called heaviest and the lot you called lightest.

Thanks again,
George

 

George, it’s been a while but I was thinking 1.5gr was the spread difference between the high group and the low group. I do not remember what the individual highest and lowest group spread was but generally I kept those fairly tight.
Again, not scientific but enough for me.
Nick

 

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.

 

Thanks for the feedback -- let me try to address these points.

> Sample size is too small

I stated that myself in the article, in that the Next Steps should include more data. You have to start somewhere to get an idea of how to do the experiment and if there is any signal in all of the noise. Remember, this is just part one of a series!

> survey size is too small

Well, I hope that you will fill out the next survey to help improve that!

> no definition of shooter type(hunter/br/prs)

It's the same rifle I've used in my previous experiments & articles. I just got tired of listing the same info over and over.

> converting to or from grams to grains does NOT AFFECT ACCURACY NOR PRECISION.

I measured in grams then converted (in a spreadsheet) because my A&D scale is capable of more precise measurements using that unit than it is with grains. Maybe I could have worded it better in the article?

 

It's true, and I wrote about that in the article with a hypothetical example!

 

I've done my own test couple weeks ago with Winchester and Federal 308win brass that was fired many times.

On Average the lighter brass has more volume than the heavier brass.
HOWEVER... this is ON AVERAGE. So there are exceptions.

Ammolytics: you did a good job at testing this. You did more than necessary to paint a proper picture.
At first quick glance, I didn't think showing 1x vs 4x fired was necessary. But once I took a good look, it was obvious that it matters.

Thanks !

 

I'm doing 75 fired .308 cases now, all prepped exactly the same and neck turned. When I get finished I'll post the results volume vs weight. It's a smallish sampling but should be interesting.

 

real life
30 oz is 13125 grains
30 oz is 850.486 grams
850.486 grams is 13125.00473 grains
a difference of 0.00473 grains over 850 grams real life
a long way from "nearly 30% coarser."(math)
50 grams weight went 50.001 which is 771.63335 grains,
50 grams went 771.64 grains
99.999% accuracy between grain and gram on the fx120i.
next time try real life

 

NOT TRUE see my post.
doing a 'test" with too small of a sample size is a waste of time.
no statistical validity.

 

I enjoyed reading your report, well written and thought out. I liked the fact that you did conditional comparison (1x vs 4x fired). This ended up proving a theory I had that multiple fired cases become more consistent.

It is not unusual to find things that you would have done differently after performing such an evaluation. That is to be expected. After all, "We don't know what we don't know", until we have tried.

Thank you for sharing.

 

I think you might be misunderstanding the point about the scale precision?
Measuring with grains, the FX120 is only capable of 0.02 grain precision, meaning it can read 0.00, 0.02, 0.04, etc.
Measuring in grams, it has 0.001 gram precision, meaning it can read 0.000, 0.001, 0.002, etc.

0.02 grains = 0.001296 grams
0.001 grams = 0.0015432 grains

It uses grams (metric) as the base measurement, then converts for the display. The display is limited, so the scale has to round up.

If I measure in grams and covert to grains, I can maintain some precision because I'm not forced to round as much:
0.001 g = 0.0015 gr
0.002 g = 0.0031 gr
0.003 g = 0.0046 gr

Conversely, if I measure in grains on the scale and wanted to convert to grams, I lose precision:
0.002 gr = 0.0013 g
0.004 gr = 0.0026 g
0.006 gr = 0.0039 g

This only matters when trying to measure really small differences and the effects aren't cumulative (it seems like you are assuming that's what we're saying).

I disagree entirely that it's a waste of time. I learned quite a bit from this experiment and I think you could as well.
Frankly, your comments are coming across as rather rude.

It took over 100 hours to do this research, pour over the data, and write it up to share with the world. How long you spend taking a dump on my work? If you'd like to prove something, then put in the same amount of effort and show your work.

 

Thanks, I appreciate it!

 

Could not agree more. If you don’t have a nice way to provide constructive feedback that grows the knowledge within this community, then close your trap!

 

I sure hope he doesnt talk to people the way his posts read. Just hit the ignore button.

Thank you for the time and effort you've put into this.

 

There was an old post on this site that I can no longer find, used to have a link but it broke in the last site upgrade, in any case, it had a comparison of case weight to case volume with 223 brass that data indicated that there was a 70% correlation between weight and volume.

 

thanks for taking the time, effort, and resources to perform this test and then print it( after compiling data)!!! some of the responses to your work is why some of the world record holders quit putting results of their testing on here, to the detriment of us all. I for one say thanks!!! bryant