Why sort cases by weight?

[Lonestar41]

Amen to your last comment.

 

[VaniB]

and it helps some of us to sleep better (you also have to remember that we, as br shooters, are eliminating variables. as many variables as we are prepared to attack.....

....this is the best explanation, making the most sense to me.


Thanks gents for all your input. I just wanted to be sure I wasn't overlooking something. This is one of the very few things I will continue to disregard in my target shooting endeavors. I am not minimizing the importance of it for those who consider it a necessary procedure in their handloading regimen. ie; To each his own.

 

[Sundown]

Well Van...When you get that flyer that spoils the one important group...you'll know what to do next time! It's always going to be in the back of your Head now!

 

[VaniB]

Why sort cases by weight?

Because it is faster than filling each case with water and checking the case capacity.

Some of us just don't like waterboarding our cases.

And my point is that I find measuring it by weight, with water, or via cookie dough is not necessary.
As already stated in my last post, thanks for your input, and I will not take it away that any sort of uniformity in precision handloading is a worthwhile step to some.

 

[Trevor60]

Look closely, you can see the ink on the paper inside the bullet holes.
Red was the lightest 5 cases in the box
Blue was the heaviest 5 cases in the box.
284 win/Norma brass/180 Berger hybirds/powder measured on FX120i/600 yards


CW

thanks for running the test
can you share the average case weight difference between the lightest and heaviest

Trevor

 

[Ccrider]

So how much weight is overweight? Asked differently, how do you weight sort?

 

[WIB3]

Sorting by weight does one thing, it tells you how much that case weighs. There is absolutely no connection in case weight and case volume. All laupa cases from the same lot will be very close in weight. The easiest way to accurately measure the internal volume of your case is to use a Burette along with some 90% isopropyl alcohol. I use a 10ml burette. A typical dasher case is about 2.75ml. Primer plugs can be purchased at 21 century.

 

[WIB3]

In cases like the Dasher, this process should be performed after the case is fully blown out, trimmed to length and fired with the primer in the case. Sonic cleaning will remove any carbon which would displace the alcohol. It all depends how much time you have and how crazy you are.

 

[Uncle Ed]

I will not challenge your explanation if you have one. I'm just trying to make sure I didn't overlook something.

How do you know if other shooters at the range are overweight?

If they step on a cat's tail and the cat dies they are overweight.

 

[Ned Ludd]

Ned,

I have been wondering when weighting cases if the cases are trimmed to a uniform length first?
What if any case prep is done before case weighting?

Thanks

Using fully-prepped, fireformed brass, I flip the primer around backwards (cup down) to prevent water from getting through the flash hole and into the primer, which is not effective "case volume". Trimming cases to uniform length should be part of brass prep, or weighing cases isn't likely to help.

The bottom line on the correlation between case weight and case volume is that some shooters will never believe that such a relationship exists, regardless of how much corroborating data is put in front of them. On the other hand, there are some that may be convinced that the correlation is valid. One group will never weight sort, the other might consider doing it. I'm tired of trying to convince those that will never believe there is a strong linear correlation between case weight and case volume, no matter what evidence is presented, so I'm not inclined to provide any further supporting data than what I already have. If you want to see some actual data, just do a search.

Even much better, if you're open-minded and curious, test case weight versus case volume for yourself. Load up 10 to 15 cases from the same prep/Lot, fire them, then determine the water volume of each fired case. I personally find it easier to weigh each of the cases before priming/loading them, but if you go that route, you have to mark or somehow keep track of each case so the volume determined after firing goes with the correct case. Plot case weight versus case volume, and have your graphing program perform a linear regression (i.e. generate the "best straight line" equation from the scatter plot data). Then you can decide whether the response appears linear in your own hands.

So how much weight is overweight? Asked differently, how do you weight sort?

Cc - the idea here is not that some cases are overweight or underweight, the idea is to sort cases by weight into subgroups that have more uniform internal volume. As I mentioned, the correlation is not perfect...in other words, not every single value in a case weight versus case volume plot will be spot on the best straight line. There will always be a few outliers. Nonetheless, if you sort your cases by weight into 3 groups, i.e. light/medium/heavy, I think you will find the internal volume within each of the weight-sorted groups has less variance than if you had done nothing at all. Simple. That's all you can really hope to accomplish when sorting cases by weight - make the internal volume of weight-sorted cases more uniform than those not sorted by any method at all. The good news is that sorting cases by weight is stupid-fast and easy, so why not do it, especially if you compete in a discipline such as F-Class, where large numbers of loaded/fired rounds per match are the norm?

With a new Lot of brass, I typically record the weight of at least 50 cases. You need a good analytical balance to do this. I'm not talking about graphing of case weight here, just visually inspecting the sample data set, which is not difficult with a list of 50 or so numbers. Go through the values carefully...find the Hi/Lo values (i.e. determine the range) and try to get a feel for the distribution of case weights within the range. At that point, you can pretty easily make choices on where to set your weight limits for each sort group. This really isn't rocket science, it's all about using some simple physics and allowing statistics to work in your favor, no different than any other sorting process used by reloaders.

 

[WIB3]

Very well done.^^^

 

[BartsBullets]

Using fully-prepped, fireformed brass, I flip the primer around backwards (cup down) to prevent water from getting through the flash hole and into the primer, which is not effective "case volume". Trimming cases to uniform length should be part of brass prep, or weighing cases isn't likely to help.

The bottom line on the correlation between case weight and case volume is that some shooters will never believe that such a relationship exists, regardless of how much corroborating data is put in front of them. On the other hand, there are some that may be convinced that the correlation is valid. One group will never weight sort, the other might consider doing it. I'm tired of trying to convince those that will never believe there is a strong linear correlation between case weight and case volume, no matter what evidence is presented, so I'm not inclined to provide any further supporting data than what I already have. If you want to see some actual data, just do a search.

Even much better, if you're open-minded and curious, test case weight versus case volume for yourself. Load up 10 to 15 cases from the same prep/Lot, fire them, then determine the water volume of each fired case. I personally find it easier to weigh each of the cases before priming/loading them, but if you go that route, you have to mark or somehow keep track of each case so the volume determined after firing goes with the correct case. Plot case weight versus case volume, and have your graphing program perform a linear regression (i.e. generate the "best straight line" equation from the scatter plot data). Then you can decide whether the response appears linear in your own hands.



Cc - the idea here is not that some cases are overweight or underweight, the idea is to sort cases by weight into subgroups that have more uniform internal volume. As I mentioned, the correlation is not perfect...in other words, not every single value in a case weight versus case volume plot will be spot on the best straight line. There will always be a few outliers. Nonetheless, if you sort your cases by weight into 3 groups, i.e. light/medium/heavy, I think you will find the internal volume within each of the weight-sorted groups has less variance than if you had done nothing at all. Simple. That's all you can really hope to accomplish when sorting cases by weight - make the internal volume of weight-sorted cases more uniform than those not sorted by any method at all. The good news is that sorting cases by weight is stupid-fast and easy, so why not do it, especially if you compete in a discipline such as F-Class, where large numbers of loaded/fired rounds per match are the norm?

With a new Lot of brass, I typically record the weight of at least 50 cases. You need a good analytical balance to do this. I'm not talking about graphing of case weight here, just visually inspecting the sample data set, which is not difficult with a list of 50 or so numbers. Go through the values carefully...find the Hi/Lo values (i.e. determine the range) and try to get a feel for the distribution of case weights within the range. At that point, you can pretty easily make choices on where to set your weight limits for each sort group. This really isn't rocket science, it's all about using some simple physics and allowing statistics to work in your favor, no different than any other sorting process used by reloaders.

Ned

You’re absolutely correct! No amount of data will sway those that think it doesn’t make a difference. No since in trying to help them out.

Weight sorting brass does make a difference. How do I know? Because I weight sort my brass, then run it over a chronograph. By weight sorting I get much more consistent numbers within the group I’m testing. Yes, this is testing Lapua brass of the same lot number 100 at a time.

Bart

 

[AJC]

....this is the best explanation, making the most sense to me.


Thanks gents for all your input. I just wanted to be sure I wasn't overlooking something. This is one of the very few things I will continue to disregard in my target shooting endeavors. I am not minimizing the importance of it for those who consider it a necessary procedure in their handloading regimen. ie; To each his own.

I do not shoot good enough to weigh for sorting. I weigh as a check for major outliers. If I have a batch of cases and I find one that is very different. Over 1gr in a 223 case I remove it from the group and mark it. When running max or above listed max I dont want surprises. I only do this in my match brass plinking ammo hell no.

 

[mikecr]

Case weight CAN correlate to capacity or to chamber fit.
But in a broad sense -it doesn't always.
One case in 20 springs back a bit differently, and correlation is lost.
If you kept only cases matching in weight, then there is potential that some culled would actually have matched in capacity, where some that you kept end up mismatching.
Such is the dynamics of this.

So given that a truth passes all tests, a rigid declaration about weight to capacity correlation cannot be truthful, as eventually tests do fail with either belief.
That is, sometimes there is correlation, sometimes not so much.

Now, is this a truth? -->The only way to know capacities are matching is to measure as such<--

 

[BartsBullets]

Case weight CAN correlate to capacity or to chamber fit.
But in a broad sense -it doesn't always.
One case in 20 springs back a bit differently, and correlation is lost.
If you kept only cases matching in weight, then there is potential that some culled would actually have matched in capacity, where some that you kept end up mismatching.
Such is the dynamics of this.

So given that a truth passes all tests, a rigid declaration about weight to capacity correlation cannot be truthful, as eventually tests do fail with either belief.
That is, sometimes there is correlation, sometimes not so much.

Now, is this a truth? -->The only way to know capacities are matching is to measure as such<--

The only way to truly know is load them exactly the same and shoot them over a chronograph and record your result. That is the TRUTH.
Bart

 

[group therapy]

i like it when people do not weigh cases, I move up the finishing order.

 

[ronemus]

I did an experiment several years ago to determine just how much effect brass weight has on .223 loads. I used WW brass (sized, trimmed and deburred, primer pockets uniformed, flash holes deburred, and neck turned) , WSR primers, charges of RL-15 or N-550 powder weighed to 0.1 gr, and 75 gr A-Max bullets. Using the lightest and heaviest cases (sorted from 1000 once-fired I had on hand), I had two lots of 10 cases with a 3 gr difference in weight. The average muzzle velocity difference was 16 fps, just a bit more than the 12 fps due to 0.1 gr of powder. I choose to sort 0.5 gr lots of .223 brass for my long range loads, but the effect will only matter at 800-1000 yards - the vertical displacement on the target from such a small velocity change is negligible at shorter distances. Unless you control all other sources of variation, the effect of brass weight is negligible. I also shoot .284, and because the brass is twice as heavy I batch in 1 gr lots.

 

[Rustytigwire]

New lc 223 from graf. Weigh 4 or 5 sets of 10. Find avg. Weigh individual cartriges.
So i save 95.5 to 96.5 and toss the outliers some up to 97 some low as 94.
Cull goes to kids plinker mix.
Keepers go to pdog buckets .
No waste.
Weigh cartridge, zero scale, charge, weigh again. Eyeball for height.
I do look for "short or tall" neck fill in every load. It still happens now and again. All same make happy.
I do not precision shoot yet but want to develop reasonable habits.
I can always mix them up again (the horror)
These forums great info great people.
Thanks
Tom

 

[group therapy]

Correct although only one sample. The segregated groups were half of the combined.

Yet the issue lies in the possibility of having 4 of the red and 1 of the blue. If those 4 reds are a killer group and then mr blue pops his little self into the equation an inch and a half away......
Maybe it woulda been a personal best or even some kinda record. But no, just another almost, that MIGHT have been prevented by sorting the brass, maybe. If you can’t tell, it helps me sleep at night

 

[group therapy]

@Dusty Stevens now I’ve gone and done it