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Working load and adjusting seating ...

Chiquita

Proud Armenian
Gold $$ Contributor
Say I have a working load and I am pretty happy with the speed, SD and ES.
I assume if I play with the seating depth to have tighter grouping the only thing that will change in my load is the speed. Theoretically the SD/ES should stay the same and only have a change in the speed, Correct?
 
^^^ Pretty much what he said . If you are pleased with your SD / ES , then changing seating depth may vary your velocity slightly , up or down . But you are looking for tighter groups now by adjusting depth . IMHO ; SD and ES are just a good guide-line for determining better brass prep , than most anything else . I've seen some really amazing scores shot with obscene SD / ES numbers . I just shot a 194 - 5x at 1,000 yards on Sunday in blustery , switchy , winds . The SD was 13.6 , and the ES was 27.8 , so take it for what it's worth .
 
It also isn’t necessarily the lower ES/SD numbers that will shoot the tightest.
I always do seating depth tests first, as well as swapping primers, if for a new barrel/rifle.
I have a load that produces 5 shots into the same hole at 200y, but the ES is well over 100fps...go figure.
Actually, I do not chrono my loads until after load development.
The final average velocity and ES is all I’m concerned with, then when I have good data points of 200 shots, I worry about SD.
Anything smaller than 30 round data is not enough to calculate a stable SD.
It’s like saying ONE 1/4 MoA group is how your rifle ALWAYS shoots. The more you shoot, the bigger that 1/4 MoA aggregate will get.

Cheers.
 
It also isn’t necessarily the lower ES/SD numbers that will shoot the tightest.
I agree.
I have a load that produces 5 shots into the same hole at 200y, but the ES is well over 100fps...go figure.
How well does this load work at 1K yards? same MOA grouping as 200?

Actually, I do not chrono my loads until after load development.
The final average velocity and ES is all I’m concerned with, then when I have good data points of 200 shots, I worry about SD.
Anything smaller than 30 round data is not enough to calculate a stable SD.
It’s like saying ONE 1/4 MoA group is how your rifle ALWAYS shoots. The more you shoot, the bigger that 1/4 MoA aggregate will get.

Cheers.
 
MrBarrel,
I have not shot that load to 1K, and never will. It is a short course 100yrd load.
It will shoot into pretty much one hole for the match, yet at 200 it will do the same if the rifle is shot slow enough.
It just happens that the bullet is exiting at the same point in vibration, nothing more.

Cheers.
 
There are at least a couple major caveats in regard to the answers to your questions. First, as you change seating depth, you will change the effective internal case volume, thereby potentially affecting pressure and velocity. The real question is how much can you alter seating depth before pressure and velocity are noticeably altered? If you change seating depth by a sufficient amount, the velocity can change. In my hands, changing the seating depth of a jumped bullet (i.e. a bullet not seated into the rifling) by .010" to .015" in either direction may typically not be enough to cause a noticeably change in velocity, or at least one that can accurately be measured by a chronograph. In other words, you may detect what appears to be very small velocity changes shot-to-shot, but the average velocity change between a 5-shot string at one seating depth and another will be less than the standard deviation, and therefore is not effectively a statistically significant change. However, changing seating depth by ~.050" in either direction can easily cause a noticeable and statistically significant change in velocity. So the total range over which you test seating depth is one caveat. The larger that range, the greater the chance that the velocity data will change. Further, if you change seating depth by an amount sufficient to change the average velocity by a certain margin, it is entirely possible that you could put the load out of the optimized charge weight window.

For example, Berger Bullets has put out a method for optimizing seating depth with VLD bullets, which are sometimes finicky with respect to seating depth, that covers an extremely wide range in very coarse increments: https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/. If covering such a wide range during seating depth testing, it is practically guaranteed that velocity will change noticeably, possibly moving the load out of the optimal charge weight window. In such an event, it would be necessary to re-visit charge weight testing within the much narrower optimal [coarse] seating depth window, before proceeding to fine-test seating depth within that narrower window in small increments. To be clear, this sort of "which is first, the chicken or the egg?" testing results are not uncommon in the reloading process. Any time your start testing too far away from what ends up as the optimal region for a given variable, it is likely you will need to re-visit that variable again once you actually optimize a different variable. The good news is that you can readily test charge weights, move to seating depth optimization, move back to charge weight testing for fine-tuning, then optimize seating depth some more. The order in which you carry out the steps isn't as critical as the final result. This kind of incremental or stepwise testing is not at all uncommon when trying to optimize multiple variables.

Another caveat lies in the group size used to determine ES and SD. For example, if you're using 5-shot groups to determine ES/SD, the values obtained can easily change from day to day on different range trips, due to the small sample size (n). A load that gave an ES/SD of 15/7 fps one day night give an ES/SD of 25/12 fps (or greater) on a different day. In other words, what you thought were nice low ES/SD values actually weren't. Again, that can happen because the sample size was so small the numbers weren't statistically significant. The more times you obtain consistent ES/SD measurements for a given load on different days using small sample sizes as the velocity data, the more reliable those numbers probably are. In fact, if one were to shoot 10 x 5-shot groups with the exact same rifle/load on a single day, making absolutely certain the rifle/barrel completely cooled between individual shots, as well as between groups, I suspect many might be surprised at how large the range of ES/SD values they would obtain might be.

To be clear, I am not advocating shooting 10 x 5-shot groups just to estimate ES/SD values. Under such circumstances, typical load development would consume far too many rounds of usable barrel life. However, one needs to be aware of the the inherent issues associated with using small samples for statistical analyses. There are some things you can do to realistically achieve confidence in your ES/SDS values during the load development process without necessarily shooting the barrel in the process. As I mentioned, compare the ES/SD values obtained using a small sample size for the exact same load on different days, just to convince yourself the nice low values you obtained for a single 5-shot group a few days prior are still holding true. Second, some F-Class shooters follow a load development regimen that consists of essentially three parts: charge weight testing, seating depth testing, and finally, load validation. Arguably, load validation may considered a different animal than load development; nonetheless, I'm lumping it in with the load development process for the purpose of this response. F-Class matches typically consist of several long strings of fire (25+ shots) throughout the course of a morning/ear/y afternoon. Because of the long strings of fire and the fact that the atmospheric conditions usually change during the course of even a one day match, low ES/SD values are generally considered highly desirable.

So let's say you've identified what looks like a good optimal charge weight using 5-shot groups. You then optimize seating depth using that charge weight, meaning however many more 3-shot or 5-shot groups you need to cover the chosen seating depth test range. As I noted previously, it is possible to change seating depth of a jumped bullet by at least .010" in either direction without substantially altering the average velocity. For that reason, you would then expect the low ES/SD values previously observed for the 5-shot group of your chosen charge weight during the prior testing step to hold up across several adjacent seating depth increments within your seating depth test range, if not the entire range. Remember, if you test across much larger seating depth increments, the velocity data likely will change. Nonetheless, the velocity data from adjacent segments of the seating depth test can be used to further support [or refute] the notion that your chosen charge weight appears to provide stable and reproducible [low] ES/SD values.

OK. So you've now identified a suitable charge weight and optimized the seating depth to tighten up the groups. So far, the velocity data are looking good, even though there is still the caveat of small sample size. So now the idea is to validate the load. For an F-Class shooter, that might involve loading up 25 rounds or so of what they believe should be the optimized load (i.e. specific charge and seating depth). Next, they would shoot several sighting shots, followed by 20 shots for record, just as they would do in an actual match, trying to maintain shooting cadence, focus, attention to conditions, i.e. do everything just like they would in an actual match. The only difference is that they're also recording velocity data. In other words, they are attempting to validate that everything their preliminary testing has suggested to be true about the load actually holds up under match conditions. If the load doesn't hold up in terms of both velocity and precision, further testing is warranted. What is "good enough" or "sufficient" can only be determined by the shooter. Sometimes, these multi-step charge weight/seating depth/load validation approaches can be painful. In that event, I always try to remember that at least a few of my competitors will almost certainly not be skipping any steps or cutting corners, which usually provides sufficient motivation to continue.
 
There are at least a couple major caveats in regard to the answers to your questions. First, as you change seating depth, you will change the effective internal case volume, thereby potentially affecting pressure and velocity. The real question is how much can you alter seating depth before pressure and velocity are noticeably altered? If you change seating depth by a sufficient amount, the velocity can change. In my hands, changing the seating depth of a jumped bullet (i.e. a bullet not seated into the rifling) by .010" to .015" in either direction may typically not be enough to cause a noticeably change in velocity, or at least one that can accurately be measured by a chronograph. In other words, you may detect what appears to be very small velocity changes shot-to-shot, but the average velocity change between a 5-shot string at one seating depth and another will be less than the standard deviation, and therefore is not effectively a statistically significant change. However, changing seating depth by ~.050" in either direction can easily cause a noticeable and statistically significant change in velocity. So the total range over which you test seating depth is one caveat. The larger that range, the greater the chance that the velocity data will change. Further, if you change seating depth by an amount sufficient to change the average velocity by a certain margin, it is entirely possible that you could put the load out of the optimized charge weight window.

For example, Berger Bullets has put out a method for optimizing seating depth with VLD bullets, which are sometimes finicky with respect to seating depth, that covers an extremely wide range in very coarse increments: https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/. If covering such a wide range during seating depth testing, it is practically guaranteed that velocity will change noticeably, possibly moving the load out of the optimal charge weight window. In such an event, it would be necessary to re-visit charge weight testing within the much narrower optimal [coarse] seating depth window, before proceeding to fine-test seating depth within that narrower window in small increments. To be clear, this sort of "which is first, the chicken or the egg?" testing results are not uncommon in the reloading process. Any time your start testing too far away from what ends up as the optimal region for a given variable, it is likely you will need to re-visit that variable again once you actually optimize a different variable. The good news is that you can readily test charge weights, move to seating depth optimization, move back to charge weight testing for fine-tuning, then optimize seating depth some more. The order in which you carry out the steps isn't as critical as the final result. This kind of incremental or stepwise testing is not at all uncommon when trying to optimize multiple variables.

Another caveat lies in the group size used to determine ES and SD. For example, if you're using 5-shot groups to determine ES/SD, the values obtained can easily change from day to day on different range trips, due to the small sample size (n). A load that gave an ES/SD of 15/7 fps one day night give an ES/SD of 25/12 fps (or greater) on a different day. In other words, what you thought were nice low ES/SD values actually weren't. Again, that can happen because the sample size was so small the numbers weren't statistically significant. The more times you obtain consistent ES/SD measurements for a given load on different days using small sample sizes as the velocity data, the more reliable those numbers probably are. In fact, if one were to shoot 10 x 5-shot groups with the exact same rifle/load on a single day, making absolutely certain the rifle/barrel completely cooled between individual shots, as well as between groups, I suspect many might be surprised at how large the range of ES/SD values they would obtain might be.

To be clear, I am not advocating shooting 10 x 5-shot groups just to estimate ES/SD values. Under such circumstances, typical load development would consume far too many rounds of usable barrel life. However, one needs to be aware of the the inherent issues associated with using small samples for statistical analyses. There are some things you can do to realistically achieve confidence in your ES/SDS values during the load development process without necessarily shooting the barrel in the process. As I mentioned, compare the ES/SD values obtained using a small sample size for the exact same load on different days, just to convince yourself the nice low values you obtained for a single 5-shot group a few days prior are still holding true. Second, some F-Class shooters follow a load development regimen that consists of essentially three parts: charge weight testing, seating depth testing, and finally, load validation. Arguably, load validation may considered a different animal than load development; nonetheless, I'm lumping it in with the load development process for the purpose of this response. F-Class matches typically consist of several long strings of fire (25+ shots) throughout the course of a morning/ear/y afternoon. Because of the long strings of fire and the fact that the atmospheric conditions usually change during the course of even a one day match, low ES/SD values are generally considered highly desirable.

So let's say you've identified what looks like a good optimal charge weight using 5-shot groups. You then optimize seating depth using that charge weight, meaning however many more 3-shot or 5-shot groups you need to cover the chosen seating depth test range. As I noted previously, it is possible to change seating depth of a jumped bullet by at least .010" in either direction without substantially altering the average velocity. For that reason, you would then expect the low ES/SD values previously observed for the 5-shot group of your chosen charge weight during the prior testing step to hold up across several adjacent seating depth increments within your seating depth test range, if not the entire range. Remember, if you test across much larger seating depth increments, the velocity data likely will change. Nonetheless, the velocity data from adjacent segments of the seating depth test can be used to further support [or refute] the notion that your chosen charge weight appears to provide stable and reproducible [low] ES/SD values.

OK. So you've now identified a suitable charge weight and optimized the seating depth to tighten up the groups. So far, the velocity data are looking good, even though there is still the caveat of small sample size. So now the idea is to validate the load. For an F-Class shooter, that might involve loading up 25 rounds or so of what they believe should be the optimized load (i.e. specific charge and seating depth). Next, they would shoot several sighting shots, followed by 20 shots for record, just as they would do in an actual match, trying to maintain shooting cadence, focus, attention to conditions, i.e. do everything just like they would in an actual match. The only difference is that they're also recording velocity data. In other words, they are attempting to validate that everything their preliminary testing has suggested to be true about the load actually holds up under match conditions. If the load doesn't hold up in terms of both velocity and precision, further testing is warranted. What is "good enough" or "sufficient" can only be determined by the shooter. Sometimes, these multi-step charge weight/seating depth/load validation approaches can be painful. In that event, I always try to remember that at least a few of my competitors will almost certainly not be skipping any steps or cutting corners, which usually provides sufficient motivation to continue.
Question for you , @Ned Ludd . Have you been following me around while I do my load development ? You literally described , in detail , what my regime is for developing and refining a load for F-class , TR . And as you stated , a consistent regime used by many F shooters . Because we are looking for that over-all consistency that works in varying conditions of shooting those strings as temperature , humidity , and winds change throughout the day . Very well written piece . Thank you .
 
I learned much of what I know of reloading from Steve Blair, a fellow shooter that also a member here at A.S. I have further added to that toolkit through a lot of reading and by trial and error. I cannot make any claim as to inventing that particular approach or any other; many folks more knowledgeable than myself had already worked them out long before, largely because they do work. Glad to hear that approach is also working for you. As with anything, the particular discipline in which someone shoots necessitates subtle, or even significant changes to the approach, but the basic idea of charge weight and seating depth testing, followed by load validation, is relatively straightforward. Of course, one could always attempt to validate a load under match conditions, but if it still needed tweaking as is often the case, their score in that match would almost certainly suffer. Much better IMO to know in advance that a developed load performs as expected under match conditions. Doing so offers the additional advantage of confidence behind the rifle when you are ready to use the load in a match for the first time.
 
Great info from Ned Ludd. One thing I've learned from this site is that one has to be open to trying new methods. I've been reloading since the mid 1980s. I've learned more in the couple of years I've been using this site than in all the previous years. Many good contributors here!

PopCharlie
 
Great info from Ned Ludd. One thing I've learned from this site is that one has to be open to trying new methods. I've been reloading since the mid 1980s. I've learned more in the couple of years I've been using this site than in all the previous years. Many good contributors here!

PopCharlie
i'm fully agree with you,the are a lot verry,verry professional and helpfull persons in here,
No doubt at all,this forum have no equals !! Again many thanks to all great contributors.
N_F
 
Thank you all for your replies.

I will print Ned's detailed post so I follow it better.
It seems I an follow & understand it better when I see it on paper.
 

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