reconsidering measuring case weight

[simplerider]

I recently read a review on some hornady brass someone had done some testing on. Their first initial thoughts were bad due to inconsistent case weight fluctuations, up to 10gr difference, and brass thickness was also inconsistent. After sorting his brass he finally starting testing and found there was no significant change in accuracy on target (500 yards if I remember correctly) between his lowest weighed and highest weighed brass while cleaning the f class target with several x's, and also stating his target puller reported only a 1 inch vertical spread.

He contacted Hornady to ask about the large variation in case weight and was told by the representative that they manufacture their brass with attention to case volume consistency rather than weight. So It got me thinking, I understand that brass weight consistency should reflect case volume consistency (theoretically), but is this all in vain? How many other manufacturers do the same making their brass? Is there a way to measure for case volume besides filling each case with water? It just makes me think that weighing all this brass is all for nothing if the inside isn't the same :-\

Further down the rabbit hole I go ;D

 

[CatShooter]

I recently read a review on some hornady brass someone had done some testing on. Their first initial thoughts were bad due to inconsistent case weight fluctuations, up to 10gr difference, and brass thickness was also inconsistent. After sorting his brass he finally starting testing and found there was no significant change in accuracy on target (500 yards if I remember correctly) between his lowest weighed and highest weighed brass while cleaning the f class target with several x's, and also stating his target puller reported only a 1 inch vertical spread.

He contacted Hornady to ask about the large variation in case weight and was told by the representative that they manufacture their brass with attention to case volume consistency rather than weight. So It got me thinking, I understand that brass weight consistency should reflect case volume consistency (theoretically), but is this all in vain? How many other manufacturers do the same making their brass? Is there a way to measure for case volume besides filling each case with water? It just makes me think that weighing all this brass is all for nothing if the inside isn't the same :-\

Further down the rabbit hole I go ;D

There are those that sort by weight and those that sort by water...

... but to actually learn something, sort some cases by whatever methods you can, and then pick batches from each and test them yourself - then you really know which method works (for you).

 

[simplerider]

Very true. Just kind of wondering why the manufacturers measure their brass consistency by one way while we (most) typically measure by another. Just brainstorming a little.

 

[CatShooter]

Very true. Just kind of wondering why the manufacturers measure their brass consistency by one way while we (most) typically measure by another. Just brainstorming a little.

It would be impossible for manufacturers to measure case volume with water (or anything else)... the better makers (Lapua, Norma) hold weight very close.

 

[jlow]

The reality is people have been known to make all kinds of wild claims and unless they show they know what they are doing and conduct a well controlled scientific study to proof their point, it is nothing but talk and we all know how reputable and trustworthy stuff we get from the web are.

A for “they manufacture their brass with attention to case volume consistency rather than weight”, this has to be total baloney. You have a fixed volume chamber and even if a manufacturer can make the case with consistent volume (which they can’t – how can it be done? Its not like they use an internal mold….), once you fire the brass and it conforms to chamber dimensions, heavier case = more brass = smaller volume. How can this be avoided? I am willing to believe anything if it can be backed up by logic and science but this has none of the above.

 

[CatShooter]

The reality is people have been known to make all kinds of wild claims and unless they show they know what they are doing and conduct a well controlled scientific study to proof their point, it is nothing but talk and we all know how reputable and trustworthy stuff we get from the web are.

A for “they manufacture their brass with attention to case volume consistency rather than weight”, this has to be total baloney. You have a fixed volume chamber and even if a manufacturer can make the case with consistent volume (which they can’t – how can it be done? Its not like they use an internal mold….), once you fire the brass and it conforms to chamber dimensions, heavier case = more brass = smaller volume. How can this be avoided? I am willing to believe anything if it can be backed up by logic and science but this has none of the above.

What he said....

 

[rogn]

? Case rim and extractor groove can and do vary, so will weight. So will volume, maybe- we need more info.

 

[CatShooter]

? Case rim and extractor groove can and do vary, so will weight. So will volume, maybe- we need more info.

If you measure the diameter of the extractor grove on a bunch of cases, and then take calculate the volume of a band of brass equal to the thicknesss of the differences of the two widest measurements... and multiply by the specific gravity of brass (~8), you will find that talking about variations of the extractor groove is a red herring in this discussion - it is nothing worth worrying about.

But if it worries you, then sort your cases, first by extractor grove variance, and then by weight.

 

[jlow]

CatShooter is absolutely right that rim and extractor groove argument is a complete red herring.

If you go to this thread that I just posted on today where I measured weight and volume difference in a batch of Lapua brass.

http://forum.accurateshooter.com/index.php?topic=3858399.45

The difference in volume between the lightest and heaviest case was 40 uL. Having worked in the biomedical research area for 30 years, I can tell you that 40 uL is no small volume that you can hide in the rim and extractor groove, it would be more like a large tumor. :

 

[mikecr]

Just measure actual capacity, or don't.
The Hornady whoever was lying to you...

 

[simplerider]

They weren't lying to me, I didn't talk to anybody. remember this was something someone else reported that just got me thinking, that's all. I never said I believed anybody on the subject, it just sparked some thoughts about reloading and making better ammo.

Interesting inputs so far, thanks everyone

 

[amlevin]

Is there a way to measure for case volume besides filling each case with water?

Yes, there is. Use powder. Take a nice fine ball powder that settles well without having to use a drop tube or vibrating. CFE223, 2000MR are two I have used with success.


Place the case on your digital scale and Tare/Zero the scale. Fill the case with the powder you've selected. I put the case in a paper bowl, standing up, and just pour powder til it overflows. Strike the powder off level with the case mouth then return the filled case to the digital scale. You are now reading the capacity of the case in grains of "That" powder. Record the weight, pour out, and repeat. I just pour the powder from the bowl that overflowed and the powder from the case into a powder pan and re-use the same small amount to repeat.

If you want you can mark each case with a sharpie and when done sort and segregate by the recorded volume as indicated by the powder weight.

Do this once and keep the 'batches" separate. Shouldn't have to do it again until you replace that batch of brass.

 

[mikecr]

Powder isn't as easy as water because of it's variances in load density, and of the powder itself.
Water is easy

 

[Brians356]

Powder isn't as easy as water because of it's variances in load density, and of the powder itself.
Water is easy

Now ya done it! Gird your loins ... :-[

 

[amlevin]

Powder isn't as easy as water because of it's variances in load density, and of the powder itself.
Water is easy

Why do you think I mentioned using a powder that settles well? (finer the better).

Water may be great but often the only benefit to using it is if you want wet cases.

 

[mikecr]

There is no need to reinvent capacity measure. But if you do, it will be with something BETTER than water, instead of yet another abstract.
The benefit of H20 is that you can determine actual H20 capacity, and with it you get consistent fill density. So easy a caveman can do it.

 

[amlevin]

The benefit of H20 is that you can determine actual H20 capacity, and with it you get consistent fill density. So easy a caveman can do it.

And yet that ever present disadvantage of having to dry out your cases afterward.

 

[jlow]

I think what I would like to see in terms of QA for using ball powder to measure case volume is measuring volume with and without something that cause the powder to settle. What I mean is if you take 10 cases and measure volume variation with the powder the normal method and then again where the powder in the case that has been vibrated to settle it (obviousely with multiple measure per case per method). If there is no significant “bridging”, then the degree of difference between the cases should remain the same.

One distinct disadvantage of using powder is you cannot obtain a true volume since to get that number, you will need an accurate density conversion value and that is very difficult to get since the volume is taken up by both the powder and air.

The case does get wet with the liquid method, but I have found that using rubbing alcohol and an air compressor can in fact clear the moisture out in record time. For that matter, I have found that an air compressor is one of the most versatile tool in the reloading area.

 

[mikecr]

Yeah I don't like getting cases wet with cleaning, or cleaning after annealing either. But I do have to once in a while.
So long as I dry them ASAP, (I blow them out and then dry vibratory clean) no problem so far.

I believe that if you're looking for an accurate measure of capacity variance, water will give it to you. Powder, sand,, or whatever? I doubt the consistency and repeatability in this matches H2O resolution. Dry media produces voids not only in their own fit but with the entire inner surface/angles of the cases, and every bit of that dry media would need to be consistent/uniform(no big or small bits) from case to case.

 

[CatShooter]

Water may be great but often the only benefit to using it is if you want wet cases.

;D ;D ;D