Sorting match cases by H2O capacity

[Dave Way]

When setting up for a new LR rifle or barrel, I normally fully prep a bunch of brass. After squaring primer pockets, trimming to length, turning necks, etc., I then wash the brass to remove all lubricant and any remaining brass particles before weighing. I start with a large enough number of cases that I can end up with matched sets which weigh within 0.1 grains.

I have never tried sorting by case volume and would like to hear from those who may have tried it. I would guess this would have to be done after the first firing once the brass had been formed to the chamber. Did you use water or alcohol? Did you notice a big variation in capacity? Were you able to correlate a difference in velocity, consistency or accuracy of loads using cases sorted this way versus unsorted cases?

Thanks-Dave.

 

[savagedasher]

I can say I do cases volume after the case has been shot twice
I made a tool that that measure off the shoulder And displaces the water out of part of the neck. Using the bubble at the top give a problem to get the same
My method I can repeat ever time on the same case .
By doing that I can get my to ES 5
Along with seating depth and primer selection
I normally can find a sweet spot of 5 to 8 thousands with no change in speed
I then do all the tuning with the tuner
Off the point of aim at 100 yards

 

[Bart B.]

I think a 1 grain spread in weight is good enough. Unless you can measure the difference between case volume of loaded rounds before firing and at peak pressure when they've expanded to maximum volume.

The variables in powder, primers and bullet release force mask smaller spreads.

Some may reason otherwise.

 

[whatwind?]

Some one once said to use alcohol instead of water because it is more consistent, less air in the liquid?

And then weight sort primers by grams

 

[savagedasher]

I can check A hundred fire form cases and never find a gr difference
60 % will be .02 difference the rest will be above and below .

 

[dmoran]

I can check A hundred fire form cases and never find a gr difference
60 % will be .02 difference the rest will be above and below.

Yet to figure out, how you can report to the hundredth (.02) in weight, when your using a tenth (.2) scale for your weighing.
But several times over several years now, you report it to the hundredths, as you did again here.

Wish I could buy brass that volume weigh out like yours do !.!.!
I'd be real lucky to get 6 out of 100 to have volumes with in .02-hundredths of each other
(but likely could get half them to be close to .2-tenths of each other).

 

[Dave Way]

Been there, done that. I've tried with water and alcohol to avoid surface tension. Then tried with salt and baking soda. But then I realized that it was like peeing on yourself while wearing a black suit. It makes you feel nice warm, but no one notices. Trying to turn 1/4 MOA ammo into 1/8 MOA is pretty futile if you can't read wind.

Joe

But if you like data here's some. Let's see if you can spot the real surprise.

View attachment 1078329

Were all the Lapua Palma cases for barrels 2,3 and 6 from the same lot? Dave.

 

[Dave Way]

The LC brass and 1st Lapua brass, regular large flash hole .308, was in the same barrel and same chamber. Barrel 2,3 and 6 were with the same Palma brass. However, barrel 6 was chambered with a different reamer. Same specs as the other reamer, but my own property, therefore inherently ever so slightly different.

The surprise was that the LC brass had less variance in case capacity. To some that may be a real surprise.

Joe

I’m assuming you had weight sorted these sets of cases prior to H2O sorting? If so do you recall how close they were sorted? Within 0.1 grain, within 0.5 grain, etc. Thanks.

 

[Dave Way]

I appreciate everyone's replies. I had hoped to find a correlation between weight sorting cases and volume sorting cases. I will test that myself as I don't see where anyone has mentioned doing that. If a correlation can be made, it may make doing both irrelevant. I assumed everyone would have different opinions on this subject and that is fine. Personally, I believe failure to sort by case volume has to be detrimental to load consistency, the question is to what extent. It may or may not be measurable.

Yes I saw the one reply about learning to read wind flags and while I agree reading the wind is critical, consider this. If you were able to read wind flags perfectly and had a 2 MOA rifle, you would still shoot 2 MOA. I would like to take a that 1/4 MOA rifle, shoot for 1/8 MOA by testing everything, AND learn to read wind flags. Why not? It's winter, not much else to do.

Now looking at the data in post #7 the case volume varied from 0.61% to 1.05% depending on the set of cases. How many of us would allow that much variation in powder charge when loading cartridges for a match? In a Dasher that could be 0.3 grains of powder, in a 300 WSM you are looking at 0.6 grains of powder. I wouldn't, in fact, I weigh charges to 0.02 grains on a FX 120-i scale.

I have also considered weighing primers and since a couple mentioned primers I just did an interesting test. I will list the results in another post in a few minutes.

Thanks for your input everyone-Dave.

 

[Jennb]

Easiest to decide for yourself. Weight out your cases, H2O sort your cases then shoot the extreme ends of these with each other!

 

[Dave Way]

That's the plan!

 

[group therapy]

@group therapy

 

[Corey Schwanz]

...Trying to turn 1/4 MOA ammo into 1/8 MOA is pretty futile if you can't read wind.

Well said. Sometimes you just have to call a load "good enough", then actually get out on the range and practice.

 

[rardoin]

Well said. Sometimes you just have to call a load "good enough", then actually get out on the range and practice.

So true! I have shot some of my best matches/scores with loads I was not overly pleased with and was worried about being competitive with...but showed up at the match anyway not having high expectations. If I can get them grouping at about an inch at 300yds (5-8 shots) I have learned my time/money is best spent at a match. (F-class)

 

[mikeeg02]

I seem to remember a thread a few months ago with graphs and plots of weight vs water capacity.


Found it. Some good information to read if you havent.

http://forum.accurateshooter.com/th...the-truth-or-somewhere-in-that-range.3892214/

 

[Ned Ludd]

I appreciate everyone's replies. I had hoped to find a correlation between weight sorting cases and volume sorting cases. I will test that myself as I don't see where anyone has mentioned doing that. If a correlation can be made, it may make doing both irrelevant. I assumed everyone would have different opinions on this subject and that is fine. Personally, I believe failure to sort by case volume has to be detrimental to load consistency, the question is to what extent. It may or may not be measurable.

Yes I saw the one reply about learning to read wind flags and while I agree reading the wind is critical, consider this. If you were able to read wind flags perfectly and had a 2 MOA rifle, you would still shoot 2 MOA. I would like to take a that 1/4 MOA rifle, shoot for 1/8 MOA by testing everything, AND learn to read wind flags. Why not? It's winter, not much else to do.

Now looking at the data in post #7 the case volume varied from 0.61% to 1.05% depending on the set of cases. How many of us would allow that much variation in powder charge when loading cartridges for a match? In a Dasher that could be 0.3 grains of powder, in a 300 WSM you are looking at 0.6 grains of powder. I wouldn't, in fact, I weigh charges to 0.02 grains on a FX 120-i scale.

I have also considered weighing primers and since a couple mentioned primers I just did an interesting test. I will list the results in another post in a few minutes.

Thanks for your input everyone-Dave.

There is a general correlation between case weight and case volume. That is, as case weight increases, case volume generally decreases. However, I have weighed cases AND determined H20 volume more times than I care to think about and there are always some outliers where case weight does NOT correspond well with case volume. The discrepancy is most likely due to variance in the depth/width of the extractor groove, and/or cartridge base-to-shoulder measurement. Either of these can alter the internal volume without changing the weight. Although sorting cases by weight will not remove the occasional outlier, I do believe you will end up with better internal case volume consistency by weight sorting cases as opposed to doing nothing at all.

Regarding the actual determination of case volume, I have read a number of responses and threads over the years where apparently folks had difficulty using water and have used all sorts of crazy tricks such as adding detergent or alcohol to the water. That is totally unnecessary. I posted a little "How To" thread about determining case volume with water some time ago, it might be helpful:

http://forum.accurateshooter.com/threads/case-volume-determination-pic-heavy.3896148/

 

[Bart B.]

Another variable is case out of round issues.

More out of round equals less capacity.

 

[savagedasher]

I fire my cases twice before I check cases volume then I don’t even size them
I found too much volume varence

 

[BartsBullets]

Here’s another thought...Instead of sorting by H20, I use my labradar to sort my brass. For the Nationals I took 100 cases, loaded them as identically as possible and checked the velocity with the labradar.

With a clean barrel I’d fire two shots to foul the barrel and get it up to speed. Then I’d start recording the velocities from the match brass. To keep up with the results I’d just write the velocity on the side of the case. Then sorted accordingly!

If you can zoom in on the cases on the table you can see the velocities on the side.
Bart

 

[mikeeg02]

Bart -

Curious, do you shoot any, but specifically the cases that are different a second time for verification?