weighing cases

[mikecr]

Am not asking how to weigh brass.

Yet the heading of your thread is weighing cases
To your questions, 'efficiency' and accuracy are different endeavors, and 'spread' is based on percentage of deviation from mean cartridge H20 volume. To predict it's affect you need QuickLoad.

 

[Ned Ludd]

unsized brass is not what you will be loading in spite the fact that quickload uses that volume.
i have never seen quickload vol correct for my brass.
do as you choose

You want to determine case volume for fired-formed brass, regardless of the method you use. The reason for this is that a fire-formed case has been expanded out to the maximum dimensions of the chamber (pressure cell). Some may argue that this can even take several firings, but in my hands, further expansion of the brass with subsequent firings is pretty minimal.

I use the average case volume from about 20 fire-formed cases as an input in QuickLoad. This input can be adjusted as needed, or when you switch to a new/different Lot # of brass. I find QuickLoad to be a valuable tool in the reloading process, although I wouldn't say it is absolutely essential by any means. What it does for me is to streamline the reloading process a little bit, thereby saving some time and reloading components. The savings aren't huge, but are there nonetheless. YMMV.

If you want to get a feel for the effect of case volume on velocity, there are a couple ways to go about it. The best way is to directly sort cases by water volume, picking out two sets with the lowest and the highest average volume from within your total volume range (i.e. low/hi extremes). Then load them up identically and directly determine the effect on velocity. Alternatively, QuickLoad, once you have calibrated it to your specific setup, will give predictions that are fairly reasonable with respect to what you actually measure using the first approach.

The bottom line is that anyone wishing to compete at the highest possible level needs to be aware of potential sources of error in their chosen discipline so that they can make informed decisions in their reloading process about which steps they consider to be the most important, and which ones may be pretty far down the list in terms of their effect on the target. In F-Class, case weight is certainly worth consideration, but it's generally not going to be up at the very top of the list, although it may be far more important in certain other disciplines. For that reason, I simply input the average case volume value into QuickLoad once, and generally continue to use that value as long as I'm using that specific Lot# of brass. I do measure case volume every time I do a new brass prep, but as I mentioned, in my hands it doesn't increase much after the first firing. If it does change, I will use the more recent value. I do not concern myself with adjusting charge weight based on case volume...it is what it is, and my load development/testing process takes that into account.

The main reason for sorting cases in F-TR is to minimize velocity excursions during the long strings (20+) of fire in a typical match. I often use 2 or 3 different weight groups of cases in a single match, but all the cases for a single string of fire come from the same weight group. Regardless of which weight group they originated, all the cases will be charged with the same amount of powder, which will have been identified as "optimal" by testing. The idea is simply to minimize velocity variation due to case volume variance within a single string of fire. As I mentioned previously, you can change case volume by a fair bit without a huge effect on measured velocity. This is really no different than changing effective case volume by changing seating depth of the bullet in a given load. Move the bullet farther into the case and effective case volume decreases, move it farther out and effective case volume increases. For bullets seated off the lands (jumped), you can move the bullet in/out a fair bit before the average velocity changes by an amount that is greater than the standard deviation of your velocity measurement. The same is true of case volume, which you will see if you load lowest/highest volume cases from a specific Lot # of quality brass. If the volume variance of that Lot # of brass is pretty reasonable, you may not even see a difference in velocity between the two volume groups (hi/lo) of cases that is greater than the standard deviation for any one velocity determination. In that event, the two numbers are not statistically different, meaning the effect of minor case volume variance on velocity is actually smaller than the typical velocity variance inherent to that load. In other words, case volume was not the limiting source of error.

Regardless, you should play around with various approaches, test the effects for yourself, then decide whether sorting brass is worth the time and effort, and/or what approach makes the best use of your time. You will likely learn something useful about how to compare different sources of error to identify which steps in the reloading process are the most critical and therefore should receive your greatest attention. Many of the things we do such as weighing powder to less than +/- one kernel, sorting bullets, or sorting cases by volume may not by themselves have a large effect on velocity variance and/or precision. However, even minor sources of error can be additive, and in some cases synergistic. So for many steps, we simply try to carry them out in the most rigorous way our reloading equipment allows, even if the limits to which we measure/weigh/sort are far below the point where variance would have any measurable effect on precision. For example, weighing powder to +/- half a kernel (which I do) can be calculated to give less than 1 fps velocity variance, an amount my chronograph is not even capable of measuring reliably. Having said that, the method I use to weigh powder to that level of precision requires little more time and effort than it would for me to weigh powder to +/- 0.1 gr. When I get behind the rifle at a match, I never, ever have to be concerned that my powder dispensing technique might become a limiting factor. Not even close. Peace of mind and confidence in your load can be worth a lot. The balance lies in knowing where your time and efforts are best spent to get the most in return. The very best way to do that is to test various parameters and determine the actual effects of variance for yourself.

 

[ireload2]

Weighing cases and checking their internal volumes does not result in directly comparable data without giving it some thought.

Water and powder have approximately the same specific gravity (that is units of weight per unit volume). Brass is about 8X times the specific gravity of water.
So variations of case weight have to be about 8X the variations in water volume to be directly comparable assuming 2 cases that weigh exactly the same will have the same volume.

For me weighing cases and graphing the data allows me to see the distribution of the weights. I can easily pick out the low outliers on the left hand tail and the high outliers on the tight hand tail.
The cases in the middle 4 sigma represent the most uniform cases.

You can set aside the outliers or sell them to a shooter who does not care about case weights.
Otherwise you can use the heavier cases for initial load work up. The light cases can serve as spares.
The cases in the middle of the distribution are your best cases.

Beware if you are offered new cases in opened containers. They may be the outliers culled from a larger group of cases. If you weigh them and find 2 humps in the distribution and a gap between humps you have culls.

I have weighed and graphed multiple lots of WW .45-70 brass and found that all 3 lots had some overlap. They were not culls but they definitely were different lots.

 

[Regnar]

You want to determine case volume for fired-formed brass, regardless of the method you use. The reason for this is that a fire-formed case has been expanded out to the maximum dimensions of the chamber (pressure cell). Some may argue that this can even take several firings, but in my hands, further expansion of the brass with subsequent firings is pretty minimal.

I use the average case volume from about 20 fire-formed cases as an input in QuickLoad. This input can be adjusted as needed, or when you switch to a new/different Lot # of brass. I find QuickLoad to be a valuable tool in the reloading process, although I wouldn't say it is absolutely essential by any means. What it does for me is to streamline the reloading process a little bit, thereby saving some time and reloading components. The savings aren't huge, but are there nonetheless. YMMV.

If you want to get a feel for the effect of case volume on velocity, there are a couple ways to go about it. The best way is to directly sort cases by water volume, picking out two sets with the lowest and the highest average volume from within your total volume range (i.e. low/hi extremes). Then load them up identically and directly determine the effect on velocity. Alternatively, QuickLoad, once you have calibrated it to your specific setup, will give predictions that are fairly reasonable with respect to what you actually measure using the first approach.

The bottom line is that anyone wishing to compete at the highest possible level needs to be aware of potential sources of error in their chosen discipline so that they can make informed decisions in their reloading process about which steps they consider to be the most important, and which ones may be pretty far down the list in terms of their effect on the target. In F-Class, case weight is certainly worth consideration, but it's generally not going to be up at the very top of the list, although it may be far more important in certain other disciplines. For that reason, I simply input the average case volume value into QuickLoad once, and generally continue to use that value as long as I'm using that specific Lot# of brass. I do measure case volume every time I do a new brass prep, but as I mentioned, in my hands it doesn't increase much after the first firing. If it does change, I will use the more recent value. I do not concern myself with adjusting charge weight based on case volume...it is what it is, and my load development/testing process takes that into account.

The main reason for sorting cases in F-TR is to minimize velocity excursions during the long strings (20+) of fire in a typical match. I often use 2 or 3 different weight groups of cases in a single match, but all the cases for a single string of fire come from the same weight group. Regardless of which weight group they originated, all the cases will be charged with the same amount of powder, which will have been identified as "optimal" by testing. The idea is simply to minimize velocity variation due to case volume variance within a single string of fire. As I mentioned previously, you can change case volume by a fair bit without a huge effect on measured velocity. This is really no different than changing effective case volume by changing seating depth of the bullet in a given load. Move the bullet farther into the case and effective case volume decreases, move it farther out and effective case volume increases. For bullets seated off the lands (jumped), you can move the bullet in/out a fair bit before the average velocity changes by an amount that is greater than the standard deviation of your velocity measurement. The same is true of case volume, which you will see if you load lowest/highest volume cases from a specific Lot # of quality brass. If the volume variance of that Lot # of brass is pretty reasonable, you may not even see a difference in velocity between the two volume groups (hi/lo) of cases that is greater than the standard deviation for any one velocity determination. In that event, the two numbers are not statistically different, meaning the effect of minor case volume variance on velocity is actually smaller than the typical velocity variance inherent to that load. In other words, case volume was not the limiting source of error.

Regardless, you should play around with various approaches, test the effects for yourself, then decide whether sorting brass is worth the time and effort, and/or what approach makes the best use of your time. You will likely learn something useful about how to compare different sources of error to identify which steps in the reloading process are the most critical and therefore should receive your greatest attention. Many of the things we do such as weighing powder to less than +/- one kernel, sorting bullets, or sorting cases by volume may not by themselves have a large effect on velocity variance and/or precision. However, even minor sources of error can be additive, and in some cases synergistic. So for many steps, we simply try to carry them out in the most rigorous way our reloading equipment allows, even if the limits to which we measure/weigh/sort are far below the point where variance would have any measurable effect on precision. For example, weighing powder to +/- half a kernel (which I do) can be calculated to give less than 1 fps velocity variance, an amount my chronograph is not even capable of measuring reliably. Having said that, the method I use to weigh powder to that level of precision requires little more time and effort than it would for me to weigh powder to +/- 0.1 gr. When I get behind the rifle at a match, I never, ever have to be concerned that my powder dispensing technique might become a limiting factor. Not even close. Peace of mind and confidence in your load can be worth a lot. The balance lies in knowing where your time and efforts are best spent to get the most in return. The very best way to do that is to test various parameters and determine the actual effects of variance for yourself.

Thanks for that. You answered what I was getting at and I agree with everything yiu said. that is why I want to measure the case volume.

You also said someting that I have have always felt but something I have not seen mentionedon the fourm before and thst is piece of mind.

When a competitor, in any sport, does not prepare themselves to the fullest, does not have the best equipment and does not prepare their equipment to perform at the highest level, will have difficulty in concentrating 100% on the,task at hand than they will be at a disadvantage to those who have prepared. 100% confidence in your equipment allows you to make accurate decisions based on your performance. whenyou have a round go out of the10, you know it was you not your equipment.

An extreame example of this is skydiving. i have almost 2k jumps. not once did I ever worry about the chute not opening. I trained for it happened and was prepared to handle the situation but I was never worried. that allowed me to concentrate on what I had to do. if im shooting and having a verticle issue, but I know I take shortcuts i would start wondering if it was caused fro my rounds or my technique and no k ow exactly how to correct it.

 

[AckleymanII]

Measure the run out in front of the web, sort cases. Good to start off with 2000 cases. You will end up with multiple batches that will last a life time.

Otherwise, it is like "piss'en on a flat rock".

 

[Bart B.]

What about sorting cases to the ones with pressure rings with even visual heights?

For example, this Remington 308 BR case has zero pressure ring height opposite its maximum height. Measuring wall thickness shows the difference.

 

[Willie]

Measure the run out in front of the web, sort cases. Good to start off with 2000 cases. You will end up with multiple batches that will last a life time.

Otherwise, it is like "piss'en on a flat rock".

Interesting! Could you please expand on this?