• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Questions about Weight-Sorting Cases

South Pender

I'm prepping new cases for my 6.5x55 and have chamfered the flashholes, trimmed them to the same length, and neck-turned them. These are Lapua cases, and I weighed 40 and found them all to be within about 1 gr. in weight--from a low of 176.8 gr. to a high of 177.9. I thought I'd sort them into two groups--the lightest 20 and the heaviest 20. If I do it this way, the weight variation in each group of 20 will be about .5 gr.

Here are my question:

1. Is this sorting worth the effort? To be sure, it didn't take much time, but if I passed on the sorting I'd have cases varying by up to 1 gr. in weight in groups shot.

2. In my two groups of 20 cases--with the variation in each of the two groups of 20 cases running .5 gr.--is this sufficient closeness in case weight for you guys shooting competitively? That is, in any group of 5 shot, the maximum case weight variation would be .5 gr., and in some groups shot, it would be less than that.
 
A lot of guys weight-sort brass. A lot of guys don't.

The premise, as Don suggests, is that weighing brass is a simple, quick way to figure out volume differences. A premise that many of us feel has never been proven with any consistency.

What you might do is take that light batch and actually measure the volume in, say, five cases. Then do that for the heavy batch.

If you see a correlation between weight and volume, there's your answer. And if you don't, there's your other answer.
 
South Pender said:
I'm prepping new cases for my 6.5x55 and have chamfered the flashholes, trimmed them to the same length, and neck-turned them. These are Lapua cases, and I weighed 40 and found them all to be within about 1 gr. in weight--from a low of 176.8 gr. to a high of 177.9. I thought I'd sort them into two groups--the lightest 20 and the heaviest 20. If I do it this way, the weight variation in each group of 20 will be about .5 gr.

Here are my question:

1. Is this sorting worth the effort? To be sure, it didn't take much time, but if I passed on the sorting I'd have cases varying by up to 1 gr. in weight in groups shot.

2. In my two groups of 20 cases--with the variation in each of the two groups of 20 cases running .5 gr.--is this sufficient closeness in case weight for you guys shooting competitively? That is, in any group of 5 shot, the maximum case weight variation would be .5 gr., and in some groups shot, it would be less than that.
Click to expand...
while back someone pit a graph up on the website plotting wt VS volume. No correlation. Will try to find the graph.
 
South Pender said:
I'm prepping new cases for my 6.5x55 and have chamfered the flashholes, trimmed them to the same length, and neck-turned them. These are Lapua cases, and I weighed 40 and found them all to be within about 1 gr. in weight--from a low of 176.8 gr. to a high of 177.9. I thought I'd sort them into two groups--the lightest 20 and the heaviest 20. If I do it this way, the weight variation in each group of 20 will be about .5 gr.

Here are my question:

1. Is this sorting worth the effort? To be sure, it didn't take much time, but if I passed on the sorting I'd have cases varying by up to 1 gr. in weight in groups shot.

2. In my two groups of 20 cases--with the variation in each of the two groups of 20 cases running .5 gr.--is this sufficient closeness in case weight for you guys shooting competitively? That is, in any group of 5 shot, the maximum case weight variation would be .5 gr., and in some groups shot, it would be less than that.
Click to expand...

Ron Blane data 23 Jun 2017
1650498366594.png
1650498399569.png
Make whatever you want from the data.
 
Webster said:
while back someone pit a graph up on the website plotting wt VS volume. No correlation. Will try to find the graph.
Click to expand...
Wow. That's really hard to believe. I wouldn't expect a perfect negative correlation of -1.0, but I'd certainly expect a strong negative correlation--maybe something on the order of -.80. It's hard to imagine how it could be any other way.

Edit. I typed the above before seeing the data. After seeing the data, I computed the Pearson correlation coefficient between (a) empty case weight in grains and (b) case volume in cc. for the 10 LC13 cases. The Pearson correlation coefficient is -.80, just as one would expect.

Next, I did the same calculation for the WCC 10 cases and got a Pearson correlation coefficient of -.795.

I didn't take the time to do the computations for the other brands of cases, but the results for them should be fairly similar.
 
Last edited:
Perhaps I can re frame the question. For you guys who do weight-sort your cases, would you consider a case weight variation of .5 gr. in a set of five you shot for group (say 6.5x55 cases weighing on average 177 gr.) to be sufficiently close in weight to eliminate case volume as a variable?
 
To measure volume I assume water is used, correct? The few times I’ve done that, I wasn’t sure how to best be consistent from one to the next, regarding surface tension; how high the water domes, etc. What advice does everyone have for me on that detail?
 
I own a M96 Target rifle and weight sorted Lapua brass two decades ago. I deburred the primer holes as well. I used 142 SMK with ( I think ) H4831. The groups were very group. That said, I can't say weighing brass made a difference because I never shot a comparison test load using brass of varying weights. I recently weight separated resized LC 30-06 brass to 7.7x58 brass, fireformed and trimmed to length. I then weighed volume weighed rubbing alcohol in each case. Case weight doesn't correspond to the same volume.
 
South Pender said:
Perhaps I can re frame the question. For you guys who do weight-sort your cases, would you consider a case weight variation of .5 gr. in a set of five you shot for group (say 6.5x55 cases weighing on average 177 gr.) to be sufficiently close in weight to eliminate case volume as a variable?
Click to expand...
Who knows!? :confused: I do it because I do it. :) And, in the past, I've sorted to the nearest grain, and to the nearest .5 grain. It generally depends on the quantity of brass that I am weight sorting, in order to come up with meaningful weight sorted batches. Awhile back, a friend and I went in together and purchased a 2,000 quantity of Lapua 6.5-.284 cases. Since I had a cold case of beer ready for the task, I agreed to weight sort the cases and share 50-50 with my friend. To make it fair, I came up with a recommended split and offered him first choice: High side or low side. Anyway, turned out I was able to sort to the nearest .1 grain. The smallest weight sorted batch on my "low side" share amounts to 132 cases (a 5x1000 match) at 193.2 grains average weight (Lot # 193.2 Lapua Shehane). Does it make any difference on paper? Who knows! Do I feel good about it? Immensely! My extraction grouves are more consistent. :cool:
 
Last edited:
dannyjbiggs said:
Who knows!? :confused: I do it because I do it. :) And, in the past, I've sorted to the nearest grain, and to the nearest .5 grain. It generally depends on the quantity of brass that I am weight sorting, in order to come up with meaningful weight sorted batches. Awhile back, a friend and I went in together and purchased a 2,000 quantity of Lapua 6.5-.284 cases. Since I had a cold case of beer ready for the task, I agreed to weight sort the cases and share 50-50 with my friend. To make it fair, I came up with a recommended split and offered him first choice: High side or low side. Anyway, turned out I was able to sort to the nearest .1 grain. The smallest weight sorted batch on my "low side" share amounts to 132 cases (a 5x1000 match) at 193.2 grains average weight (Lot # 193.2 Lapua Shehane). Does it make any difference on paper? Who knows! Do I feel good about it? Immensely! My extraction grouves are more consistent!
Click to expand...
That's only because you lived them with beer when cutting them. That's cheating!
 
first it is another step in removing small variables.
the real question is can you and your rifle tell the diff ??
so what are you shooting ?
for my competition rifles i sort to the smallest practical.
plus or minus a tenth on my current adg 300 wsm brass over 100 pcs.
( you have to buy a lot and sell off what does not sort well)
i have actually done plus or minus 0.05...a half of a tenth.
there is no quality brass in the earlier charts.
the miniscus on the water surface can easily be brought to near flat by touch with a tissue to wick off small amounts.
 
Rsadams said:
For my accurate loads I weight sort brass and bullets and have seen improvement in my groups but it may be of course just all mental but if it makes me more confident so be it...
Click to expand...
A lot can be said for the mental game. I also weight sort cases and
bullets. Winter was hard this year so it helps pass the time. Now I just
shot a .628" group at 500 yards and repeated with .871" group using
this method. I wonder if they would have been tighter if I weight sorted
my BR2's.....?? We'll save that argument for another day !!
 
Don,
The Bison Armory capacity die: https://bisonarmory.com/bison-armory-case-volume-gauge/

Very interesting! Looks like two pcbs each having a pressure sensor. Are they just measuring the air pressure inside the case, from the point where the case seals to the die surfaces on the upstroke? If so, how consistently can one case seal to the next? At the same height I mean, etc. Maybe I’m missing some important detail.
 
You must log in or register to reply here.

Similar threads

Effects of Case Weight Variation on Accuracy
2 3 4
Replies
67
Views
8,645
South Pender
Bullet Sorting
2 3 4
Replies
77
Views
7,462
Mulligan
Mulligan
sorting cases by velocity?
2
Replies
25
Views
2,534
mikecr

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Classified Ads

Forum statistics

Threads
166,274
Messages
2,215,648
Members
79,518
Latest member
DixieDog

Share This Page

Back
Top