Weight of brass versus internal capacity

[kyreloader]

I have not weighed my brass in the past and segregated it based on weight. I could not convince myself that the weight of the brass had much to do with the internal capacity of the brass. So I decided to measure the weight and internal capacity of my cases and see if the weight of the cases correlated to the internal capacity of the cases. So I took 53 Lapua 6.5x47 cases fully prepped[annealed, resized, trimmed, chamfered, tumbled-(resized with spent primer in place-use separate decapping die as last step)] and using H335 powder measured all the brass for internal capacity.

The cases internal capacity averaged 50.347g of H335 powder with a ES of 1.3g and SD of 0.314. The average weight of the cases was 215.547g with ES of 1.9g. I then figured out the correlation coefficient to be an R=-0.14174. An R of -0.3 to -0.1 shows a WEAK strength of relationship. An R of -0.1 to 0.1 shows no relationship.

As my numbers shows, weight and internal capacity show a WEAK relationship and I would argue that there is no utility in weighing cases with the thoughts that it correlates to internal capacity.

At least I have measured out the 20 cases with the same internal capacity to use for my varmint league cases. We will see if it makes any difference in my shooting.

Just thought I would share my little non-scientific experiment.

 

[Rtheurer]

Proved again...

If you get the fancy to try doing it with some Winchester brass or other domestic brass that would be a good test as well.

Thanks for sharing.

RussT

 

[Erik Cortina]

The brass has to be fire formed in chamber completely, very clean, and not resized before measuring volume.

 

[DRNewcomb]

Why would you use powder to measure the capacity, rather than water? My experience with powder is that you can get wildly different volumes by simply tapping it.

 

[kelbro]

Why would you use powder to measure the capacity, rather than water? My experience with powder is that you can get wildly different volumes by simply tapping it.

Same experience here. Water is very consistent.

 

[kyreloader]

Why would you use powder to measure the capacity, rather than water? My experience with powder is that you can get wildly different volumes by simply tapping it.

I chose powder because of the surface tension of the water, also how do you know you have the same meniscus on the top of the case each time?

In my technique, I did the same thing each time and measured each case three times to get the same measurement.

 

[kyreloader]

The brass has to be fire formed in chamber completely, very clean, and not resized before measuring volume.

Erik, the brass had been fireformed in my chamber approx 10 times.

My question is why?

I only tumble my brass. I resize my brass prior to loading it using a Warner custom FL sizing die. I understand that the fireformed clean brass that has not been resized will have more capacity, but why is that capacity number more important. Also, are you then arguing that there will then be a correlation between weight and internal capacity?

 

[mr45man]

I find that alcohol works really well. The 90 proof, if and when you spill
on the scale or outside of the brass, it dries fast and its easy to get
a good reading at the case mouth.

Makes little tiny drops out of a syringe and in the 10 seconds it takes to read the scale,don't tell me its going to evaporate and give a error
in the weight.
John H.

 

[Erik Cortina]

The brass has to be fire formed in chamber completely, very clean, and not resized before measuring volume.

Erik, the brass had been fireformed in my chamber approx 10 times.

My question is why?

I only tumble my brass. I resize my brass prior to loading it using a Warner custom FL sizing die. I understand that the fireformed clean brass that has not been resized will have more capacity, but why is that capacity number more important. Also, are you then arguing that there will then be a correlation between weight and internal capacity?

No, it will be more consistent.

Tumbling does not clean the brass thoroughly enough to conduct such a test IMO.

 

[kyreloader]

The brass has to be fire formed in chamber completely, very clean, and not resized before measuring volume.

Erik, the brass had been fireformed in my chamber approx 10 times.

My question is why?



I only tumble my brass. I resize my brass prior to loading it using a Warner custom FL sizing die. I understand that the fireformed clean brass that has not been resized will have more capacity, but why is that capacity number more important. Also, are you then arguing that there will then be a correlation between weight and internal capacity?

No, it will be more consistent.

Tumbling does not clean the brass thoroughly enough to conduct such a test IMO.

What will be more consistent? Internal capacity or weight of my case? Also, why do I need a clean case if I dont routinely shoot a clean case(in your eyes)?

I am trying to find the internal capacity of the case as I am going to reload it to shoot.

I am not trying to argue, just trying to figure out your thoughts.

 

[Erik Cortina]

The brass has to be fire formed in chamber completely, very clean, and not resized before measuring volume.

Erik, the brass had been fireformed in my chamber approx 10 times.

My question is why?



I only tumble my brass. I resize my brass prior to loading it using a Warner custom FL sizing die. I understand that the fireformed clean brass that has not been resized will have more capacity, but why is that capacity number more important. Also, are you then arguing that there will then be a correlation between weight and internal capacity?

No, it will be more consistent.

Tumbling does not clean the brass thoroughly enough to conduct such a test IMO.

What will be more consistent? Internal capacity or weight of my case? Also, why do I need a clean case if I dont routinely shoot a clean case(in your eyes)?

I am trying to find the internal capacity of the case as I am going to reload it to shoot.

I am not trying to argue, just trying to figure out your thoughts.

The internal capacity would be more consistent.
You can't get all cases dirty by the same amount, but you can clean them by the same amount.

 

[Raythemanroe]

I really don't understand the point of this thread, are people arguing That a lighter case doesn't have more capacity? My question would be where is it lighter at? Why weigh your cases for capacity and not for consistency instead or uniformity...I could see weighing different Lot or brands of casings for capacity cause manufacturers very some...

 

[jamesh]

I really don't understand the point of this thread, are people arguing That a lighter case doesn't have more capacity? My question would be where is it lighter at? Why weigh your cases for capacity and not for consistency instead or uniformity...I could see weighing different Lot or brands of casings for capacity cause manufacturers very some...

Typically a lot of the variability in the weight is in the extractor groove so that will not correlate to variation in case capacity. There may be some correlation between case capacity but it is certainly not consistent. If you want to segregate your brass by volume then measure the volume not the brass weight itself.

Listen to Donovan he spends an incredible amount of time doing this stuff.


James

 

[Erik Cortina]

I really don't understand the point of this thread, are people arguing That a lighter case doesn't have more capacity? My question would be where is it lighter at? Why weigh your cases for capacity and not for consistency instead or uniformity...I could see weighing different Lot or brands of casings for capacity cause manufacturers very some...

Typically a lot of the variability in the weight is in the extractor groove so that will not correlate to variation in case capacity. There may be some correlation between case capacity but it is certainly not consistent. If you want to segregate your brass by volume then measure the volume not the brass weight itself.

Listen to Donovan he spends an incredible amount of time doing this stuff.


James

Just because you spend a lot of time doing something doesn't make it true. ;D

I'm not saying it's wrong either, all I'm saying is that I don't check internal volume, I just weigh my cases, and it has worked for me so that's what I do. I don't have the time to check volume on 500 cases at the time.

 

[kyreloader]

I really don't understand the point of this thread, are people arguing That a lighter case doesn't have more capacity? My question would be where is it lighter at? Why weigh your cases for capacity and not for consistency instead or uniformity...I could see weighing different Lot or brands of casings for capacity cause manufacturers very some...

Typically a lot of the variability in the weight is in the extractor groove so that will not correlate to variation in case capacity. There may be some correlation between case capacity but it is certainly not consistent. If you want to segregate your brass by volume then measure the volume not the brass weight itself.

Listen to Donovan he spends an incredible amount of time doing this stuff.


James

Just because you spend a lot of time doing something doesn't make it true. ;D

I'm not saying it's wrong either, all I'm saying is that I don't check internal volume, I just weigh my cases, and it has worked for me so that's what I do. I don't have the time to check volume on 500 cases at the time.

I am arguing that I am wasting my time weighing my cases if I am trying to segregate based on case internal capacity.

Some people believe they are separating their cases by weigh as a surrogate marker for internal capacity, I am arguing that isn't the case with the brass I am shooting.

Glad your system works for you.

 

[jlow]

I have done some studies to show corrolation between brass weight and volume. You can see it here:

http://forum.accurateshooter.com/index.php?topic=3792724.msg36102321;topicseen#msg36102321

 

[gunnermhr]

After reading all of this, I think the question still remains. If there is a difference in the volume of the case how much does it affect accuracy. I think there is a great variable here and it needs to be tested on a individual basis. Point Blank, mid range and long range I think will all have different results, as well as the chambering of the rifle. Personally I weigh my cases, I don't know if it helps a whole bunch but it gives me piece of mind. I did pull 3 cases of the lowest weight and 3 of the highest weight in my 6BR and 300WSM. If the weather ever breaks I intend to shoot them at 300 yards and see if there really is a difference. I hope to see all 6 of each caliber go into the same group but I won't be surprised to see 3 go low and 3 go high. If that's the case I also expect the difference in the 3 shot groups to be greater in the 6BR than in the 300WSM. Unfortunately the weather still sucks to bad for me to give it a try anytime soon, maybe the end of March I will venture to the range and post the results. If the groups hold tight in both calibers we'll stretch them to 500 and 1000 yards and see what happens.

 

[Raythemanroe]

I feel I shoot better groups sorting brass for weight.. Should a person Trim to same length before sorting by weight?

 

[Erik Cortina]

I feel I shoot better groups sorting brass for weight.. Should a person Trim to same length before sorting by weight?

Yes, do all your brass prep before sorting.

 

[memilanuk]

Donovan,

Have you ever compared the velocities from cases that were sorted by weight vs. sorted by volume w/ H20 vs. sorted by volume w/ H380? Every twice in a while I start to wonder if some of the things we measure actually translate into a measurable difference once the bullet leaves the barrel... part of me says it has to, while another part thinks it might be lost in the noise 95% of the time.

Good info, thanks,

Monte