Reloading: Case weight does NOT accurately reflect case volume... - Page 2

Reloading: Case weight does NOT accurately reflect case volume...

This is a discussion on Reloading: Case weight does NOT accurately reflect case volume... within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I am suspicious what's causing the anomalies between weight and volume is combustion residue left in the cases. The residue would likely take up some ...

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Thread: Reloading: Case weight does NOT accurately reflect case volume...

  1. #16
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    I am suspicious what's causing the anomalies between weight and volume is combustion residue left in the cases. The residue would likely take up some volume without increasing the case weight by much.

    These cases were cleaned in an ultrasonic cleaner and it seems to do a pretty good job on the insides, but maybe not as good as I thought. I have some that were cleaned in a pin tumbler, if I have the inclination and time, I might run the same test on some of those cases.

    I think what we see from this, and remember, this is for reloaded cases as opposed to new, is that measuring case weight does NOT accurately indicate case volume. On some cases it does, on others it doesn't.

    What we would need in order to be confident that case weight was correlated to case volume is to see the correct effect around 90% (or better) of the time. We don't see anywhere near that in the data I posted.

    In fact, would you conclude that you could depend on case weight to accurately indicate case volume? Would you pick a range where perhaps there was some correlation and throw the cases away where there was not correlation? Of course not
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  2. #17
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    Since correlation has come up, let me say a few words about what that might mean to us.

    We can think of correlation as a measure of how closely related pairs of data are. For example, if the case volume goes up and the muzzle velocity goes down EVERY time the correlation, or correlation factor, or correlation coefficient, would be -1. "1" is the best something can be; the minus sign indicates one gets smaller as the other gets larger.

    For the data I posted in the OP, Excel calculates the correlation at -0.66, but what does that mean to us or how do we use it? Let's think about the weather. The weatherperson predicts a 66% chance of rain - will it rain? Hmmm...., When will it rain? All day, sometime during the day? There's a good bit of uncertainty beyond the 66% chance of rain predicted.

    That's kinda like the -0.66 correlation of the data. .66 IS 66%. So the best we can count on is there is a 66% correlation in the data. Can we rely on that? Do you take your umbrella for a 66% chance of rain? Ever see it not rain when 66% is predicted? Moreover, it means there's a 34% chance it won't rain.

    One of the differences between the chance of rain and correlation factor is the correlation calculation does some averaging. Average always reduces the extremes which can give us a bit of a misleading impression. What only shows up in the data is where we can clearly see raw disproportionate differences. For example, the case weight may go up a bit, but the case volume goes down a lot - i.e. more than it should.

    So considering that I'm concerned with reducing those sporadic spreads, SD and correlation are not that useful to me for now. It's quite possible, and I have had a number of these, to have decent SDs but awful extreme spreads. The way that can happen is for a number of shots to be very close to the average and one shot much lower or higher than the average.
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  3. #18
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    You grossly misunderstand research and probability. You can't make such detailed individual remarks about such data. You grossly misunderstand natural variances. One can not make such details from one point of data to the next. There's more to statistics than just pointing out averages and standard deviations. There's also MUCH less than being able to explain away individual differences. My graduate research professor would have ripped your results to shreds as you make gross conclusion errors because you don't understand the limits of statistical analysis, especially based on outliers. You expect a nice tight line, but that is NOT what one gets from nature. You need to look at trends. Your graph shows a reasonably stable volume from about 99.2 to about 99.6.

    You also say you left the primers in, I assume used primers. Try it with new primers, as you are also measuring the volume of the empty primer, which could also have a small variance. I seriously doubt you will see a significant change, but it might smooth things out a little more. Also a more repeatably consistent volume measurement may also level out your data.
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  5. #19
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    Quote Originally Posted by RedSafety View Post
    You grossly misunderstand research and probability. You can't make such detailed individual remarks about such data.
    I don't misunderstand research or probability. This is not research or probability. Probability deals with the likelihood that something will happen based on previous experience. I made no claim nor calculation about probability. I simply looked at a data set of 20 samples to determine if there was a strong correlation - there really isn't. Even Excel calculates the correlation at -0.66.

    But again a correlation calculation uses averages which smoothes out extremes that I am specifically interested in, so correlation over the entire set of data is of far less importance to me than the extreme variations. It is the extreme variations I'm trying to minimize. Therefore I do need to look at the individual data points to see what's happening where.

    Quote Originally Posted by RedSafety View Post
    ...You grossly misunderstand natural variances. One can not make such details from one point of data to the next.
    This has nothing to do with natural variances, and I do understand natural variances. I even have several control data sets I compare test data to. One of which is a buddy's reloads that give much better results than I'm getting so the goal for me is to find out why that is so.

    Quote Originally Posted by RedSafety View Post
    ...There's more to statistics than just pointing out averages and standard deviations. There's also MUCH less than being able to explain away individual differences.
    Of course that's true, but that has little relation to what I'm trying to do.

    Quote Originally Posted by RedSafety View Post
    ...My graduate research professor would have ripped your results to shreds as you make gross conclusion errors because you don't understand the limits of statistical analysis, especially based on outliers. You expect a nice tight line, but that is NOT what one gets from nature. You need to look at trends. Your graph shows a reasonably stable volume from about 99.2 to about 99.6.
    Your professor would appreciate the limitations we shooters have to work with and understand that we have to work with limited numbers of data samples and still analyze results in a meaningful way.

    Why would he rip my results to shreds? Results are what it is, data is data, it is what happened. He would have no reason to rip the results.

    I have not made gross conclusion errors. I look at the data and see numerous anomalies. I do not see from the data something that is reliable or consistent enough to depend on to predict future outcomes.

    Expect a nice tight line? Why would you say that? I haven't said anything about a tight line. I did NOT and do NOT expect a nice tight line. I had hoped that the case weights would be more indicative across all the ranges than they were and had hoped that heavier case weights would at least push the velocity faster and vice versa. But the data shows not even that holds true across all the ranges of weights. So that was a bit disappointing.

    But I would never expect a tight line - that's just not realistic.

    It is true that there are some portions of the data that looks better than others, but that means there are other areas where the data indicate opposite results occurred. And it does open the possibility that if I use only the cases in that one range, that case weight might, not will but might be close enough. But it remains that we cannot conclude from this one test that the range you identified as stable is repeatable or consistent.

    But what is consistent is the inconsistency throughout the data so we cannot assume that case weight accurate reflects case volume. There are some areas that it appears so, but others that it does not.

    So, contrary to previous thinking, this shows at best we have to measure and select those areas where the case weight better reflect case volume. And somehow we have to show that those results are repeatable and consistent in that range. Which again, says we cannot just say that weight is a good indication of case volume. We actually don't know that those areas you point out, speaking of hand picking, would be repeatable.

    Quote Originally Posted by RedSafety View Post
    ...You also say you left the primers in, I assume used primers. Try it with new primers, as you are also measuring the volume of the empty primer, which could also have a small variance. I seriously doubt you will see a significant change, but it might smooth things out a little more. Also a more repeatably consistent volume measurement may also level out your data.
    You really think, given the size/volume of a 223 case, that the miniscule difference in volume due to a fired versus new primer volume is is going to change the consistency of the results?

    How do you know my volume measurement isn't repeatable and consistent? I used a syringe and a magnifier to set the water level in each case. You have a better way? I'm listening.
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  6. #20
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    Let me see if I can clarify this a bit. I have a bunch of fired Lapua cases. I am experiencing extreme spreads that a number of my buddies that reload are not getting. So in an effort to analyze this problem, my approach has been to keep all the factors I have control over constant and change one and see what happens.

    Using QuickLoad indicates the most variation comes with case volume variations. I had heard that case weights were a good indication of case volume. So I weight sorted cases and that didn't help. That raised the question, "What if case weight really doesn't reflect case volume - especially on reloaded cases?"

    So I weighed each case and measure each volume. The data showed distinct inconsistencies. Enough so that I could not trust weight alone. While there are a few weights that seem to reflect volume to a degree, I have no idea if that would be repeatable.

    But how do we use this info anyway?

    Typically we wind up with a lot of fired brass. So, believing that weight defines volume and volume defines pressure, which in turn, determines velocity, we measure case weights and sort by weight.

    I typically start with the lower case weights and reload. As I reload more, I move up to heavier cases, but still weight sorted, and so on it goes until I have used all the cases in that group.

    However, from this test (OP) the data reveals some good and some not good areas of weight and volume relationships. My engineering background says this is too small to draw conclusions from, but I'm having a hard time convincing myself I should go through more time and agony measuring case volumes.

    About the only thing I think we can conclude from this one test is that there are a significant number of data points that do NOT support using weight for volume indications. While there are some data points that seem more consistent, we don't know if they would always be consistent. We could very well come back with another set of cases that show just the opposite.

    Hence the only real thing this test shows is that there are inconsistencies in the relationship of case weight and case volumes.
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  7. #21
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    Guys, I want to apologize for letting this become something it never was. It is NOT a statistical problem. We don't even need statistics of any kind to see what's going on in this test sample.

    We can clearly see from the data that there are a number of discrepancies. There are a number of data points with the reverse of what was expected. There is a narrow range that is a bit closer to expectations, but we are very limited in what we can conclude from this data. First what we cannot conclude.

    1- This data does not represent all case weight/volume relationships. What that means is that if we see one range that looks close to what we expect, we can not conclude that range would be the same with another set of cases.

    2- Even though there is a narrow range where things look close to expectations we cannot conclude that all cases in this weight range will be the same as these. Meaning, another test might show this close range to be totally different and the other ranges might be the close ones.

    What we can conclude - and again statistics is not required in any way.

    1- We can get inconsistent results using case weights to accurately reflect case volumes. There are just too many inconsistencies over the entire data set to ignore.

    That's about it. Any other conclusion is just not supported by the data set. Without more testing all we know is what we see. And what we see is inconsistencies are significant in the data.

    Seeing the inconsistencies, for me, means that I cannot have the confidence I want by using weight as a reliable indicator of volume.
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  8. #22
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    What are your shooting buddies doing differently that they don't get these spreads?

    I've always heard of separating cases by brand and weight, but I've never bothered to do so. Well, brand sometimes. If you're getting that much variance using one brand, maybe sorting by weight isn't that important.
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  9. #23
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    Quote Originally Posted by OldVet View Post
    What are your shooting buddies doing differently that they don't get these spreads?
    Good question! I'm not sure, but we are working on some answers to that.

    Thing is, we're both using the same reloading techniques; we have different presses and dies and he shoots a 6 dasher and 6 BRA (I think on that last one).

    I don't think the press would make the difference, that doesn't eliminate the possibility, but the cases get sized correctly, at least I measure them and the base to shoulder is very close. The only other thing the press does is seat the bullet. Just doesn't seem like a press would operate as inconsistently as I see. And, I've used two different presses.

    The dies could be an issue, but again it would seem like a die would at least be consistent, but it's still in play as a contributor until I know for sure where the problem actually lies.

    But the caliber - I'm really wondering if the 223 vs the larger 6 mm cases are part of the problem. Maybe the 6 - 6.5 mm cases designed for long range are made to tighter specs and the lowly 223 cases are not given as much attention.

    And it could be the AR platform. Sooo, what we're doing, starting today, my buddy is breaking out his 12.5" AR and loading some rounds for it. We'll try his reloads in both his and my AR and I'll duplicate his loads and we'll do the same with my loads. If it's the gun, it should show up; if it's me, it should show up.

    Quote Originally Posted by OldVet View Post
    ...I've always heard of separating cases by brand and weight, but I've never bothered to do so. Well, brand sometimes. If you're getting that much variance using one brand, maybe sorting by weight isn't that important.
    That's certainly a good point!

    My buddy uses Lapua brass and swears all his numbers went down by nearly half when he started loading with Lapua cases. So that got me to try Lapua. But again, he's loading long range calibers.

    And, you're right about the sorting. My buddy does NOT sort his cases by weight. He gets amazingly low numbers.

    The reason I ran the weight/volume test was to see if there was significant variation in case volumes and how much volume differences would affect velocity. The cases (reloaded cases) do vary in volume significantly. It looked like that would be the largest contributor to velocity variations. Unfortunately, to me, my data for the 20 cases does not show a consistent, reliable relationship. Seems almost random as well as inconsistent.

    So for now, I'm not going to sort by weight or volume. Even if that's the largest contributor - volume sorting is just too much trouble and weight sorting isn't that easy either.

    It will sure be interesting to see what happens with our AR comparison tests!
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  10. #24
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    I failed to address this adequately and I think I need to because it does reflect some positive thinking but unfortunately it's also misleading. It also shows how elusive a problem like this can be. At the end I'll give 5 things that could change case volume without modifying the weight.

    ...You also say you left the primers in, I assume used primers. Try it with new primers, as you are also measuring the volume of the empty primer, which could also have a small variance. I seriously doubt you will see a significant change, but it might smooth things out a little more. Also a more repeatably consistent volume measurement may also level out your data.
    Let's say that there would be a significant difference in fired primer volume and new primer volume. What would that really mean? It would be one more reason why using case weight does not accurately represent case volume. It means that IF this were true, in order for case weight to accurately represent case volume one must use new primers.

    Second, since all the cases had the same primer, and all primers had been fired, why would the volume of a new primer be relevant? Perhaps because primers fired in different guns might have a different burn rate and therefore have different weight and/or volume? If that affects case volume or weight, then that's yet one more reason why there can be inaccuracies in using case weight for case volume.

    So what can cause these unexpected case weight to case volume relationships?

    1- residue left in the case even though it's been cleaned. These cases were cleaned in an ultrasonic case cleaner. While it does a good job when I look in the case, it is NOT nice and shiny like new cases. I can clearly see "darkness". It wouldn't take much residue to affect volume. IOW, the residue takes up space. OTOH, because the residue does not have near the density of brass, the weight of the case due to residue would not be affected nearly as much. This could make a light case have less volume.

    It is also reasonable to think that due to the case position in the US tank, the amount of residue remove/remaining may be inconsistent. For example, cases near the bottom of the tank where the US transducer is located may get more agitation than those near the top of the pile. Also some of the cases could get more water in them depending on case orientation and those with more water internally may be affected differently than those with less water. All this could leave varying amounts of residue that take up space in the case but don't add much weight.

    2- a dent in the case would affect volume but not weight. While it is easy enough to inspect cases for dents it must be done or the dents could cause a weight/volume discrepancy like we see in the data.

    3- Case elongation. While all the cases were sized before measuring there remains a phenomenon that could increase volume and not increase weight at all and is not visibly detectable. As I sized cases, some simply would not go in the RCBS shell holder; some went with a little drag; some very freely with wriggle room. My buddy loaded some of my cases to get a comparison of his loading to my loading with the same components. The results were essentially the same, but he too noticed the varying fit of some of the cases to the the shell holder - same shell holder I use. What's going on?

    Here's what's causing that. I load near and even beyond max pressure levels, as do many reloaders. But I carefully examine the cases for pressure signs then give them to my buddy and he examines them. I typically use a magnifier to get a good look. We see no significant pressure signs. What's this got to do with anything? It's the pressure, in spite of pressure signs not showing up in the primer or impressions on the case base from the bolt face. How do I know? Why does the groove of the rim get so tight it won't go in the shell holder? The case is getting elongated by the pressure. The case expands under the high pressure. In some cases the pressure exceeds the elasticity of the brass and the brass does not return to it's previous dimension. We know this happens or why would we need to resize? What we may not have realized is that the same pressure that expands the case, also can elongate the case. Specifically, the rear of the case is being compressed into the rim groove, that's why it doesn't fit the shell holder.

    So since I shoot ladders, i.e. 5 rounds per charge and typically 5-7 different charges, the charges are ever increasing and hence some cases are exposed to more pressure than others. When we don't take case elongation into account, we can have a case(s) with increased volume but no increase in weight.

    So here's is yet another reason why weight can inaccurately reflect case volume and can also explain some of those unexpected case/volume ratios we see in the data.

    4- case bulging. I was at the range the other day and another buddy mentioned some of his reloads wouldn't chamber. I asked him if he crimped with the seating die or used a separate crimp die. He said he crimped with the seating die. I knew immediately what is problem was. I looked at his problematic cases just in front of the rim and there it was, hardly visible - case bulge. When you crimp with a seating die, if you get a bit too much crimp, and it doesn't have to produce and unusually heavy crimp, the downward force on the case can cause the case to bulge just in front of the rim. The bulge, as in this case, can be quite subtle. But it was enough to keep the case from fully chambering. That would definitely be enough to change case volume without affecting case weight. I have ruined a couple of cases trying to crimp them in a seating die.

    5- case compression: I have used three different sizing dies looking for the best results, Hornady Custom, Hornady Match, and RCBS Small Base dies. I now use the Hornady Match because the other two squeeze the case too much. As another reloader described it to me, it looks like you've added a small "belt" to the case just in front of the rim groove. He's right, that's what it looks like. What's happening is the sizing die over sizes the case. But since the case can't be fully inserted into the die, the part that doesn't get resized remains at a larger diameter than the sized part of the case.

    This is yet another thing that can modify case volume without changing case weight. And this effect may be very subtle depending on several factors.

    When we consider that all these things and maybe more I haven't mentioned, accumulate in the same direction, called "tolerance accumulation", it can have significant effects on the case weight/volume ratio. Tolerance accumulation simply refers to tolerances, such as those mentioned above adding up. They can also cancel one another. So there are numerous factors to consider before we throw the baby out with the dishwater.

    As for the more consistent volume measure...I appreciate the thought, I really do. But, I was extremely careful and consistent in my procedure of filling the cases. I wiped the outsides to make sure now drops were clinging to the outside of the case. I wiped the rim groove for the same reason. I used a small syringe to top off the water level while observing the level through a 2.5x head magnifier. I made sure as I wiped the cases I did not allow the paper towel to come in contact with the top of the case to eliminate any possibility of water being wicked away by the towel. I made sure my finger(s) did not come in contact with the top of the case which would also wick water away. I did all this in one continuous session to minimize, if not eliminate, scale drift. What else can I do?
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  11. #25
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    Any chance that bubbles are adhering to the inside case walls? Did you add some soap to the water?
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  12. #26
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    Quote Originally Posted by CavemanBob View Post
    Any chance that bubbles are adhering to the inside case walls? Did you add some soap to the water?
    That is a possibility; I did not use soap.

    But, two things. One I filled all the cases exactly the same way, so it would be reasonable to think air bubbles would be fairly evenly distributed throughout the cases, There could be exceptions, but that brings us to two, the data shows things going in the wrong direction in some cases, which would be hard to explain with air bubbles.

    And I guess a third thing is the only thing I think is of value from the test is the apparent randomness of the changing wt/vol ratios. While that could be due to bubbles, I'm seeing a similar randomness in velocities. For example, just this afternoon, I saw that same puzzling effect in the 40 rounds I fired today.

    It was actually 8 incremental charge weights with 5 shots per charge.

    Notice in each one of these there is one shot that is low. The ES for the three from top to bottom are, 26, 37, and 27 - not horrible but more than I think it should be for the method I use to reload.

    Notice also that in each of the first three groups there is one low velocity outlier. If I exclude the outlier from each group the ES drops to, 10, 30, and 9.



    Then here's two more sets:

    Notice once again each set has a low velocity outlier. These have ESs of 23 and 40. The 23 isn't so bad, still not as good as it should be.

    Without the outliers the ES becomes 12 and 18. Both of those are below my goal of ES of 20 or less



    There were some exceptions but 5 out of 8 sets showed this same low outlier - some worse than others, but all out there enough to take the ES higher than it should be.

    One of the sets had an ES of 19 and an SD of 7.3 which is getting pretty close but the numbers, especially the ES is higher than what it should be.

    I have a theory that "checks all the boxes" but it's late and the theory is long and it's late (for me) so I'll post the theory tomorrow.
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  13. #27
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    For what it's worth I found this in another forum:

    "Iíve read in several places, maybe even here, that weight sorting had no bearing on internal case volume. Not consistently anyway.

    The most recent article I read took two brands and weight sorted the cases. After that they volume checked them. The tightest weighing cases had the biggest volume discrepancy while the ones that had the most weight change had the most consistent water volume. Go figure?"


    From another forum:
    "With cartridges & lot to lot brass I've tested I did not see direct correlation between case weights and capacities. So now I only act on H20 capacity."

    And another:
    "Here is a recent set of cases for which I measured water volume and prepared a graph. The number of cases was not large (15 total), but is fairly representative of what you will usually find if you carry out the same exercise, which is that there are always a few outliers that can be very far off the trend line of the scatter plot. The negative slope trend line certainly tells you that as case weight increases, volume generally decreases, but the outliers and relatively poor Pearson's R for the trend line also demonstrate that weighing cases will never be a perfect substitute for actually determining case volume. Testing a greater number of cases will certainly improve the fit, but the outliers will always be there."

    I'm sure I could find others of the same nature. All three indicate there are issues with case weight accurately predicting case volume. I'm not sure measuring case volume directly (instead of using weight) is gonna help as much as I thought anyway. Even if I had seen what I had hoped to see, I'd still have to confirm it by shooting. And, I'm working on something that may be a better approach - more tomorrow.
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    After giving this some more thought, I remembered that I had done a 5x5 with new Sig cases. The results were about the same as the 3x loaded Lapua cases, so that maybe blows my theory. But, according to my buddies, non-Lapua cases can have wide volume/weight variations so...

    The theory was that there it is volume differences in some cases that there were enough in numbers to be randomly, but consistently distributed throughout the cases. Looking at the above charts, it looks as if the outliers are significantly slower than the other 4 in the same group. The theory can even explain the large and small discrepancies, and even the good number groups.

    I'll be as brief as I can. The nature of the velocity spread is essentially one round out of five is an outlier significantly slower in velocity than the other 4. Further, it seems that this spread is due to something I'm doing. That is, my buddies load the same way and while they do get spreads they are much tighter than mine. I have eliminated the gun as the problem because I've seen the same thing in two bolt guns and three ARs. This just almost has to be something I'm doing or not doing that's different than my buddies.

    What I came up with "checks all the boxes" so to speak. Here it is. I typically load a 5x5 set. Five charges of five shots per charge. I push the pressure limits. My buddy and I closely watch for pressure signs and see nothing of consequence. I changed presses and along with that I changed to a RCBS shell holder. I started noticing a lot of fired cases would not slide into the RCBS shell holder. To see what would happen if my buddy loaded my components, I gave him 25 cases, primers, bullets, and the powder I was using. He too found some of the cases very difficult to slide into his RCBS shell holder. And, his reloads produced about the same results as mine. So it isn't me! It almost has to be the cases. Bullet weight variations of +/- 0.2 would not cause the wide velocity variations, nor would seating depth variations of +/- 0.002" - according to QuickLoad.

    That's when it hit me - it almost has to be the cases. I believe those problematic cases are the cases that are exposed to the higher charge levels. Force exerted by pressure is equal in all directions. We know that the pressure expands the cases or why would they have to be resized? What we may not realize is that pressure can expand the case in another directions - it's length. What if the higher pressures are forcing the case to expand into the rim groove of the case? That would make the case not want to slide in the shell holder. Although I have not confirmed this and don't know that I can (I've thrown all those cases out), I suspect that also increases the volume of the case because the dimensions have changed. A given charge in a given area will produce a consistent pressure which will produce a consistent force on the bullets, which will accelerate the bullets to very near the same velocity. That's exactly what's happening with my buddies's loads - they are seeing fantastic numbers/consistency.

    Further, they are not pushing pressure limits like I am. None of their cases resist sliding into the shell holder!

    So does this explain things - yes! But at this point it's just hope and a theory. Here's what it answers:

    1- I'm seeing this problem and my buddies are not.
    2- My buddy loads using all my components, the same I'm using, we get the same results I get.
    3- I have problems getting some cases to slide in the shell holder and so did my buddy
    4- This one needs some explanation. Why are some 5 shot strings showing excellent results, some are fair, and some are just awful?
    I almost always shoot a 5x5 array, i.e. 5 incremental charge weights of 5 shots each. Once shot, all the brass is dumped into a container. When I get a hundred or more, I clean them and reload them. So let's realize that in this mix of brass on a 1 to 5 ratio, these cases have been exposed to five different charge levels. Some levels high enough to elongate the case. IF that increases the internal volume, it would lower the pressure and hence the volume. Since these elongated cases would be present throughout the cases, there is a high probability of one showing up in every charge level of the next reloads. It's also highly probable that I pick 5 cases in one group that does not have an elongated case, and that's when I see the very low numbers.

    Further all combinations of charge levels can show up in any given 5 shot group. That would explain why some groups can be excellent, some fair, and some awful.

    It has to be something. The fact that my buddy and I see the same results when reloading my with my components indicates it isn't me or my reloading method. I'm hoping, since I/we have eliminated everything else, I can substainiate the theory, but my confidence level is quite low as nothing I've tried changed anything.

    This does look promising though - it does fit the strange results.

    I happen to have 20 new Lapua cases and many more new Sig cases. I am going to pick one charge where I got good numbers and load 20 rounds with Lapua cases and 20 rounds with Sig cases and measure them. The Sig is just a tack on. My buddy said when he switched to Lapua cases his numbers went down. So I'll see how the two match up.

    The nagging thing here is I've shot a LOT of new Lapua brass trying to figure this out, and it too gave similar results to what I'm seeing. But, hope springs eternal they say, so maybe knowing what to look for will be the key.
    CavemanBob likes this.
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    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

  15. #29
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    Regarding trying different primers. I've been using Federal 205M primers but day before yesterday, I bought 100 CCI BR-4 primers. Before I could even try them, my buddy showed up at the range yesterday with a set loaded with BR-4 primers!

    He chrono'd them against his normal Federal 205M primers and found the SD to be exactly the same - great numbers! But, the CCI's produced velocities 30 fps faster.
    CavemanBob likes this.
    We don't have a gun problem in the US, We have a people problem.
    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

  16. #30
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    I should add this, the guy that said,

    "Here is a recent set of cases for which I measured water volume and prepared a graph. The number of cases was not large (15 total), but is fairly representative of what you will usually find if you carry out the same exercise, which is that there are always a few outliers that can be very far off the trend line of the scatter plot. The negative slope trend line certainly tells you that as case weight increases, volume generally decreases, but the outliers and relatively poor Pearson's R for the trend line also demonstrate that weighing cases will never be a perfect substitute for actually determining case volume. Testing a greater number of cases will certainly improve the fit, but the outliers will always be there."

    Included the following plot of his test. Notice the points vary and appear to be all over the place, but the scales are pretty tight. If you look close enough you can also see, just like in my data, opposites, i.e. case wt goes up, vol goes up. Other points are the opposite, case wt goes up or down and the volume goes in the opposite direction.

    bmcgilvray and CavemanBob like this.
    We don't have a gun problem in the US, We have a people problem.
    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

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