Case weight vs internal volume

J E Custom

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Shooters going roundy-roundy about it over here also: Weighting brass ?


This is one of those subjects that will never get a 100 % agreement on and it really doesn't matter
anyhow. because everyone has there opinion and will not change as long as they think there way
or opinion is correct.

I for one am convinced that there is merit in anything that can be proven to be an improvement.

There are lots of other things that improve accuracy that some will think is a waste of time and that's there choice.

I don't think it's an argument, just a discussion and at least everyone gets to hear many different
opinions and can make up there own mind.

J E CUSTOM
 

Mikecr

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I agree.
What I've learned in many forum years is that there are truly few truths in reloading.
Even common notions rarely pass tests across the boards.

I guess I didn't keep record of my past H20 testing,, which is frustrating.
I searched around a bit and found an old BRC thread where a shooter posted his findings with (45) 308WW cases. It appears to me that he did a pretty good job, and so I graphed his results.
To chart correlation in scale, I subtracted 95gr from all brass weights while leaving H20 raw.

He has decent capacity variance for the cartridge, .5grH20, which would theoretically contribute 12fps spread in this cartridge. The brass weight itself varying 1.5gr. He could pick a mean in brass weight, or capacity, and it looks to me like he would end up with about the same number of cases(~30,30). If he chose 30 matching in capacity, his brass weight would not match & vice versa.

It would be very interesting to see other tests like this, with other cartridges.
 

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J E Custom

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Messages
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Location
Texas
I agree.
What I've learned in many forum years is that there are truly few truths in reloading.
Even common notions rarely pass tests across the boards.

I guess I didn't keep record of my past H20 testing,, which is frustrating.
I searched around a bit and found an old BRC thread where a shooter posted his findings with (45) 308WW cases. It appears to me that he did a pretty good job, and so I graphed his results.
To chart correlation in scale, I subtracted 95gr from all brass weights while leaving H20 raw.

He has decent capacity variance for the cartridge, .5grH20, which would theoretically contribute 12fps spread in this cartridge. The brass weight itself varying 1.5gr. He could pick a mean in brass weight, or capacity, and it looks to me like he would end up with about the same number of cases(~30,30). If he chose 30 matching in capacity, his brass weight would not match & vice versa.

It would be very interesting to see other tests like this, with other cartridges.


Different results from different people are the reason that opinions vary on what's best or what is a good method.

Being a stickler for details and end results I compared all of the different methods and settled on one that was beneficial but could be done in a timely manner. At the time I was shooting competition
and burning up 400 to 500 rounds a week. so time was an issue.

Lots of my competitors would tell me this was a waste of time and that was a waste of time, and all you had to do was shoot a lot(Practice) to win.(Most would not tell there secrets because they wanted to win and thought if they divulged anything you would become there competition.

So I believed nothing I heard and only half of what I saw, and started testing every aspect to see
what made a difference and what didn't.

One of these things was volume testing of the cases. Here is what I found.

I started testing for consistency in one case with water and found that It was not consistent because the water needed to be treated. I would add water to the case and weigh it, then empty it and dry
it and allow it to reach ambient temperature and fill it again. armed with these results, I started trying different additives to the water and found the best consistency/results was with a wetting agent and de-mineralized water. This was a pain and having to mix chemicals with water was an
issue. so I tried other liquids. different oils, solvents and even paint thinners. all worked but had there own problems.

Next I tried to use different powders to check for volume and found this was inconsistent also. I found the best results using the finest/smallest Ball powder available but it would rarely repeat
using the same case.

Weighing was another method I experimented with and found its strengths and weaknesses.
I found that all cases had to be sized or fire formed, trimmed (Very precisely to length) and
the flash hole de-burred inside and cleaned well to have any hope of consistency. NOTE: this was necessary on all other methods tried also.

What I found with all of this was. NOTHING WAS PERFICT and the choice was mine on which way I wanted to go.

I did prove to myself that consistency in volume made a difference in SDs and ultimately accuracy if everything else was done correctly in the loading process.

So IMO the method is not as important as the quality of your process and the fact that you want better results and are willing to doo all of the other things required to improve your accuracy.
The best Smith and equipment in the world cant help poor ammo and vise versa.

J E CUSTOM
 

phorwath

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Location
Alaska
What I found with all of this was. NOTHING WAS PERFECT and the choice was mine on which way I wanted to go.

I did prove to myself that consistency in volume made a difference in SDs and ultimately accuracy if everything else was done correctly in the loading process.

So IMO the method is not as important as the quality of your process and the fact that you want better results and are willing to do all of the other things required to improve your accuracy.

J E CUSTOM

Nice. Thanks for that backup information. Very few log the time and details to reach a confident conclusion.
 

Kennibear

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This thread has fascinated me for many reasons but the experience all have shared is priceless!

Couple of observations:

1) The case head has an extractor groove and if there is the slightest variation in uniformity of the groove case to case that will toss the volume of cases of the same weight off.

2) Brass springback is not uniform. Think about how much effort is put into the case neck (annealing, turning etc.) to make bullet release uniform. Does anybody do the same for the case body? I submit that fire formed or full length sized there is case dimensional differences from the same lot of cases after sizing or fire forming because of slight tolerances in case hardness. This has to show up in the H2O weight. Very small case diameter variations would drive the H2O volume off measurably.

3) From my Honors Chemistry class at San Jose State I remember the time spent teaching us how to fill and read the graduated cylinders by reading the meniscus. Even the room temp made a difference when you work to an overall accuracy of 0.1%. Did you fill the cases until they were flat across the neck or was there a slight convex hump of water surface tension?

I personally used to weight sort cases of the same lot. They didn't shoot noticeably better than random batches from the same lot but "it couldn't hurt". But after this thread I am really facing a conundrum.

KB
 

Mikecr

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Location
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Yeah rim differences, and springback variance are probably the main factors in measured volume to weight mis-trends. And capacity measure isn't the easiest chore on the bench.

I manage water tension with a few drops of alcohol in the water, and I touch meniscus at the case mouth with a tissue corner to flat.

It's good to review our efforts now & then and consider whether we're helping or hurting ourselves. I think we tend to assume our extra efforts help,, that they are better than normal efforts(being beyond them). But this isn't always true.
Bullet bearing comparison comes to my mind as an example of this. But that's another thread..
 

Barrelnut

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End of the Oregon Trail
This thread has fascinated me for many reasons but the experience all have shared is priceless!

Couple of observations:

1) The case head has an extractor groove and if there is the slightest variation in uniformity of the groove case to case that will toss the volume of cases of the same weight off.

2) Brass springback is not uniform. Think about how much effort is put into the case neck (annealing, turning etc.) to make bullet release uniform. Does anybody do the same for the case body? I submit that fire formed or full length sized there is case dimensional differences from the same lot of cases after sizing or fire forming because of slight tolerances in case hardness. This has to show up in the H2O weight. Very small case diameter variations would drive the H2O volume off measurably.

3) From my Honors Chemistry class at San Jose State I remember the time spent teaching us how to fill and read the graduated cylinders by reading the meniscus. Even the room temp made a difference when you work to an overall accuracy of 0.1%. Did you fill the cases until they were flat across the neck or was there a slight convex hump of water surface tension?

I personally used to weight sort cases of the same lot. They didn't shoot noticeably better than random batches from the same lot but "it couldn't hurt". But after this thread I am really facing a conundrum.

KB

Yeah rim differences, and springback variance are probably the main factors in measured volume to weight mis-trends. And capacity measure isn't the easiest chore on the bench.

I manage water tension with a few drops of alcohol in the water, and I touch meniscus at the case mouth with a tissue corner to flat.

It's good to review our efforts now & then and consider whether we're helping or hurting ourselves. I think we tend to assume our extra efforts help,, that they are better than normal efforts(being beyond them). But this isn't always true.
Bullet bearing comparison comes to my mind as an example of this. But that's another thread..

I imagine day to day barometric pressure fluctuations could even affect this. Especially if all volume measurements of the brass lot were not done on the same day.
 

barnesuser28

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Joined
Mar 2, 2012
Messages
2,820
Location
ND
Next we will be arguing about which patch material we use when cleaning gives the best accuracy. :rolleyes:
 

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