Case weight vs internal volume

Mikecr

Well-Known Member
Joined
Aug 10, 2003
Messages
5,821
Location
NC, oceanfront
I get the impression that weighing brass is done as another 'shortcut' out there.
We're tempted to generalize our shortcuts, reaching for value in them,, especially where we can't do what we really want(bad planning).

The objective here is to reach consistent capacity.
Now, when you're sorting cases by weight, what happens to those culled that would otherwise match the mean capacity of your lot? And what happened to the objective here?
I say you're better off not weight sorting, where case capacity and weight don't directly correlate.
Since the only way to determine the correlation is to measure both weight(shortcut) and capacity(our objective), you might as well just focus on capacity.

Many here shoot very large capacity cartridges that are not of modern design. Those that have to be heavily sized, trimmed, annealed, they don't last long, etc. These will never reach stable dimensions, and capacity matching of them is not viable.
Weight matching here is still as likely to do more harm than good. So don't do it, or change your plan.
 

benchracer

Well-Known Member
Joined
Dec 18, 2009
Messages
1,636
I get the impression that weighing brass is done as another 'shortcut' out there.
We're tempted to generalize our shortcuts, reaching for value in them,, especially where we can't do what we really want(bad planning).

The objective here is to reach consistent capacity.
Now, when you're sorting cases by weight, what happens to those culled that would otherwise match the mean capacity of your lot? And what happened to the objective here?
I say you're better off not weight sorting, where case capacity and weight don't directly correlate.
Since the only way to determine the correlation is to measure both weight(shortcut) and capacity(our objective), you might as well just focus on capacity.

Many here shoot very large capacity cartridges that are not of modern design. Those that have to be heavily sized, trimmed, annealed, they don't last long, etc. These will never reach stable dimensions, and capacity matching of them is not viable.
Weight matching here is still as likely to do more harm than good. So don't do it, or change your plan.

These are all very interesting comments. One of the cartridges I am playing with, .375 H&H, definitely fits into the latter category. I am planning to take some capacity measurements on fired Lapua 6.5x55 brass to see how consistent the case volume is with those, as well. The other two cartridges I plan to investigate are 22-250 in multiple headstamps and Nosler Custom brass in .264 WM.

One of the things I want to try to determine is how sensitive each cartridge is to changes in case volume, in both absolute volume and in terms of percentage. I have been playing with QL a bit to get an idea of how tightly I need to control case volume to stay within the ES bounds that I am looking for. I realize anything I get from QL is not gospel and will require real world verification. However, I am intrigued by some of the numbers QL is spitting out.

With the powders and bullets I intend to use, the sensitivity to case volume changes does not appear to be proportional to overall case volume. Based on actual fired case volume measurements from my rifles, for instance, the difference in case capacity between my 375 H&H and my .264 WM is only about 6.7 grains. Yet, QL predicts that the .264 WM will be much more sensitive to changes in case volume than the .375 H&H. I look forward to investigating further.
 

J E Custom

Well-Known Member
Joined
Jul 29, 2004
Messages
10,720
Location
Texas
Weighing cases is not perfect method to get volume consistency but it is a very good way if it is done correctly. and it accomplishes what you want.

Cases must prepped before weighing to get reasonable results.
1= clean as good as possible in side and out.
2= If they are brand new, size, clean (To remove sizing lube) de bur the flash hole inside, and
trim case necks to the same length.
3= weigh each case and sort by 1 or less grain increments.

The very best SDs have always been the cases that were the exact same weight with very little
loss if the cases were within 1 grain.

The theory behind weighing is that the brass being the same density and physically the same size on the outside, If the weight is the same , it should have the same internal volume. The fly in the ointment is that the manufacture does not all cut the extractor grove the same, but it does not seam to effect the accuracy very much if any.

I have tried all other methods and found them to be time consuming and messy. weighing is neither
so the chances are better that weighing will get done and improve your SDs.

Just my opinion

J E CUSTOM
 

Mikecr

Well-Known Member
Joined
Aug 10, 2003
Messages
5,821
Location
NC, oceanfront
I have tried all other methods and found them to be time consuming and messy. weighing is neither so the chances are better that weighing will get done and improve your SDs.
Measuring volume is more difficult than weighing, therefore weighing works?
We're tempted to generalize our shortcuts, reaching for value in them,,
Yep
 

The Oregonian

Well-Known Member
Joined
Jul 20, 2012
Messages
1,725
Location
Missoula, Montana
Measuring volume is more difficult than weighing, therefore weighing works?

I think it is a question of available time, and the priorities for that time.

I don't think anyone is saying that measuring volume is matched in effectiveness by weighing. I think what folks are asking is whether it is better than doing nothing.

You are continuing to beat the drum of 'measuring should be done bc it is better'...given unlimited time, or depending on the objectives (I.e. when marginal returns are diminishing significantly), that may be true, but not always the right path for everyone.

So I think the real question for you Mike, is whether it is better to weigh, knowing it is not a perfect substitute for measuring, or to do nothing WRT measuring or weighing.
 

benchracer

Well-Known Member
Joined
Dec 18, 2009
Messages
1,636
So I think the real question for you Mike, is whether it is better to weigh, knowing it is not a perfect substitute for measuring, or to do nothing WRT measuring or weighing.

I think the core questions that have to be examined are:

What is the objective?

Which technique is appropriate to the stated objective?

Simple weight sorting will get you to a certain point. Exactly where that point is, I don't know. It is still too early in the learning curve for me to have any answers of any kind. In fact, I am still refining my questions to help me to arrive at better answers. That is the reason for this entire discussion.

For those that have dealt with this issue, I am interested to know what was done and what the results were.

I believe that what Mike is getting at is that weight sorting only takes you so far. If the ultimate requirement is maximum precision and maximum consistency, there is no way around actually measuring case volume. I don't believe he is saying that weight sorting isn't appropriate for any purpose or circumstance.

In the end, I hope to have some hard data that will tell us something about what is really needed to achieve a given objective. For starters, though, it's good to hear from those with relevant experience. At this stage, the discussion (and formation of a hypothesis) is the important part.

The REALLY interesting part of the debate will come when we have actual data to argue over. :D
 

Mikecr

Well-Known Member
Joined
Aug 10, 2003
Messages
5,821
Location
NC, oceanfront
I would not take any actions out of assumption.
I think that until you know there is a direct correlation between weight and capacity, for a given lot of brass, it would be imprudent to cull cases based solely on weight. This, because it is possible that some of the same weight cases actually depart in capacity, while some of those culled would have matched a mean in capacity. In this scenario you could be better off taking no actions at all.
So weight sorting cases may not be 'better than nothing'. It could be worse than nothing.

I know that capacity measure is not meaningful for every chamber & reloading plan.
And it takes a plan.
You can't just pull new cases from a box and verify matching capacities(they don't). New brass also does not shoot the same as fireformed brass. You can't just go to FL sizing and expect them to match(they won't). You have to first take disciplined steps to get them matching, and even after all that effort, some won't match. Some will need to hit the trash can.
In a situation where stable case dimensions cannot be reached, and capacity measure means little more than moving target, you could just weigh them and then shoot them, to see if there is direct & significant enough correlation between case weight and chrono readings. Some of this is chamber & load dependent.
This would actually be better than nothing.
 

phorwath

Well-Known Member
Joined
Apr 4, 2005
Messages
7,355
Location
Alaska
As Mike mentioned earlier, I too have found brass curly cues inside cases that were weighed and weighed too heavy, compared to the average weight. I looked inside the casing and found a significant mass or brass drilling debris. I presume this was from the flash hole drilling, as it looked just like shavings from a drill bit.

I've also weighed different brands of brass to identify those with less case capacity, which required more or less powder to keep MV similar. R-P brass versus WW brass for example, when I wasn't seeking benchrest accuracy.

It would make sense that weighing would ID differences in case capacity with brass of the same manufacture and lot number. I would expect the exterior dimensions and extractor groove to be cut similarly.

Full disclosure: I don't have vast experience confirming MV versus variance in casing weights. I have seen the difference where I was measuring 5 or more grains difference in casing weight between different brands of brass. The heavier casings yield higher pressure and MV.
 

J E Custom

Well-Known Member
Joined
Jul 29, 2004
Messages
10,720
Location
Texas
As Mike mentioned earlier, I too have found brass curly cues inside cases that were weighed and weighed too heavy, compared to the average weight. I looked inside the casing and found a significant mass or brass drilling debris. I presume this was from the flash hole drilling, as it looked just like shavings from a drill bit.

I've also weighed different brands of brass to identify those with less case capacity, which required more or less powder to keep MV similar. R-P brass versus WW brass for example, when I wasn't seeking benchrest accuracy.

It would make sense that weighing would ID differences in case capacity with brass of the same manufacture and lot number. I would expect the exterior dimensions and extractor groove to be cut similarly.

Full disclosure: I don't have vast experience confirming MV versus variance in casing weights. I have seen the difference where I was measuring 5 or more grains difference in casing weight between different brands of brass. The heavier casings yield higher pressure and MV.


I Personally like to buy and prep 2 to 300 cases at the same time and of the same lot

This gives me a good batch ratio and normally I end up with 3 or 4 different batches of the same weight. Out of 300 I expect 5 or 6 cases that are beyond acceptance in one of the batches.

The better the quality of the brass the less number of batches and rejects.

The fact that these cases are beyond the limits of any batch does not mean they cant be used. I
use them for break-in , fowling shots and COAL gages that go in with the dies (For different bullets).

I load one batch at a time and when they are worn out, I discard that batch and start using the next batch. this keeps the consistency of the loads at there best.

Again; the cases must be prepared as mentioned earlier before any weighing takes place for it to be a useful process. (The same goes for volume testing).

I have proven to my self that weight sorting or volume testing "Does" help And improves the Standard deviation Over none weight sorted or volume tested cases. But I have not seen any improvement In SDs from weight sorted to volume tested cases.

There is however a slight increase in velocity with the smaller volume/heaver cases with the same powder charge.

To see what any rifle will do, after I find the best load/bullet/primer combination I will find at least 10 cases that weigh the exact same and shoot them for group, velocity and Standard Deviation they always do slightly better than the cases within 1 grain of each other.

Ether way does make a difference and is worth the effort. especially for very long shots.

If you are shooting/hunting 1 to 200 yards it make very little difference and may not be worth the effort to some.

J E CUSTOM
 

texastrophy

Well-Known Member
Joined
Aug 12, 2010
Messages
80
Location
Texas
IMO. Weighing brass is a COMPLETE WASTE OF TIME. When I measured capacity which is really what affects the accuracy, I found that, had I gone by weight, I would have tossed at least half of the accurate brass that I had and when I measured by weight, I found that I really should have tossed half the brass. So, if you can afford to toss good brass, go ahead and weigh it (which, by the way, will NOT give any hint of accuracy), otherwise, measure capacity or cull it when you shoot it which also has too many variables. Weight has ABSOLUTELY NOTHING to do with the internal volume of the brass!
 
Last edited:

jfseaman

Well-Known Member
Joined
Apr 8, 2012
Messages
4,171
Location
California Central Coast
Your opinion would be better received if you stated that it was your opinion.

Unfortunately physics and the experience of others contradicts your opinion.

What each of us does with our experience is an individual choice.

For you sorting brass may not return the gains you would measure to justify the effort.

For someone else it could be therapeutic, return just enough improvement to be satisfying.

Weighing brass is a COMPLETE WASTE OF TIME. When I measured capacity which is really what affects the accuracy, I found that, had I gone by weight, I would have tossed at least half of the accurate brass that I had and when I measured by weight, I found that I really should have tossed half the brass. So, if you can afford to toss good brass, go ahead and weigh it (which, by the way, will NOT give any hint of accuracy), otherwise, measure capacity or cull it when you shoot it which also has too many variables. Weight has ABSOLUTELY NOTHING to do with the internal volume of the brass!
 

phorwath

Well-Known Member
Joined
Apr 4, 2005
Messages
7,355
Location
Alaska
Weight has ABSOLUTELY NOTHING to do with the internal volume of the brass!

It does when there's drill cuttings inside the case that's identified by excessively increased case weight. And it does if the accuracy one's pursuing in case volume is relaxed. Some cases weigh 10 grains more than others. They have less internal volume.

If you goal is case cropping by capacities varying by a molecule, weight could have little to nothing to do with internal volume.
 

J E Custom

Well-Known Member
Joined
Jul 29, 2004
Messages
10,720
Location
Texas
IMO. Weighing brass is a COMPLETE WASTE OF TIME. When I measured capacity which is really what affects the accuracy, I found that, had I gone by weight, I would have tossed at least half of the accurate brass that I had and when I measured by weight, I found that I really should have tossed half the brass. So, if you can afford to toss good brass, go ahead and weigh it (which, by the way, will NOT give any hint of accuracy), otherwise, measure capacity or cull it when you shoot it which also has too many variables. Weight has ABSOLUTELY NOTHING to do with the internal volume of the brass!


Nothing is a waste of time if it improves SDs and accuracy!!!!!!

And everything you said is incorrect. There are several different ways to achieve consistent case
volumes and weighting is just one of them. some believe that weighting the volume with powder
is better. is that a waste of time also?

I have one question to ask, what medium do you use to measure volume?

Just wanting to see if I have missed something.

J E CUSTOM
 

Recent Posts

Top