Vertical Dispersion - Weighing Primers

Discussion in 'Reloading Forum (All Calibers)' started by MikeMcCasland, Mar 3, 2020.

  1. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Hey Guys,

    I'm not looking to start a debate on the merits of weighing primers, or if it's worth the time investment. I've already decided to give it whirl, and I've weighed out 1,000 of them into groups separated by .02gr mostly (with some extreme outliers culled entirely).

    I will say I was pretty surprised by a couple of observations. First, there was way more variation than I was expecting to find. I had a range from 2.28gr all the way up to 2.52gr. Most fell right around 2.40-2.46gr; nice little bell-curve.

    It's not my intent to mix any weight groups; just going to load all those that weighed the same together.

    That said, I'm not going to get a chance to shoot these until my next match, but as of late I've been struggling a bit with vertical in my load. It'll hold 10-ring vertical consistently at 1,000, but it's not as good as I see from some of the top guys.

    I've played around with depth in .002 graduations, but can't seem to tune it any tighter, so here we are. I think my powder node is on point as I'm in the usual velocity range for my barrel length/bullet combo, and generally speaking the gun is shooting quite well.

    My question: To those that have weight sorted primers, how much (if any) improvement in vertical did you see?

    Bring on the discussion; my body is ready. ;):D

    Components:
    200.20X
    N150
    Lapua Plama - turned .014"
    CCI 400s
    .0015 'interference fit'
    AMPed every firing
     
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  2. dmoran

    dmoran Donovan Moran Silver $$ Contributor

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    IME your 10% variation in weight is a fairly significant amount, and likely will reap some award from your efforts !.!.!
    How much vertical gain will depend on the distance, but regardless likely you will see less bad fliers (not exclusive to vertical dispersion alone).

    Will suggest to you: to save the extreme's from both ends, then when you have time shoot/test the lightest 5 primers against the heaviest 5 primers at your intended distance, to find out an extent and amount of dispersion indifference. Doing so as a 10-shot group/string, alternating each shot between the two extremes, would be the fairest way to test the scenario - IMO.

    Just my 2-cents...
     
  3. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Thanks for the response, and I tend to agree that it'll yield some improvement. I am also fairly confident that culling out the few extreme outliers directly translates into a point gain.

    My problem is I don't have a 1,000 yard range with pits/e-targets that easily accessible. I'm working on correcting that though. For now I'm relegated to testing under match conditions.

    I have examples of the gun holding an X-ring vertical at closer distances (500/600), but 1k is where I'm seeing more than I think a 'top shooter' would accept. Not sure if that's an indication of wind conditions playing havoc at greater distances, gun handling habits, or the load. I guess we'll find out soon enough.

    I will say sorting is easier & less time consuming than originally expected.
     
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  4. mikecr

    mikecr

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    Measuring a broad combination of attributes rarely leads to credible conclusion.
    Here, with no idea what a weight difference would come from in primer construction, if mattering, or consistent, or consistently mattering, I don't see how you could act on the results.
     
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  5. tvaught

    tvaught

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    This won't directly answer your question regarding primers...but instead brings up a different perspective.

    BLitz speaks of the required precision at shorter ranges or smaller sample sizes to satisfy a precision requirement at longer ranges or of larger sample sizes

    For example, to have 95% certainty that all 20 score shots fall within a 6" vertical span at 1k, you'd need to have a load developed that consistently printed .36 MOA for 4 shots at 1k, and .39 MOA for 5 shots at 1k. If you wanted all 20 score shots to fall within the X ring, now that shrinks to .30 MOA for 4 shots at 1k, and .33 MOA for 5 shots at 1k.

    If you don't have ready access to test sample groups at 1k, he's got another forumula for extrapolating distance.

    As an example, if 300 yards is your accessible test distance, than the the above .36 MOA 4 shot group at 1k would need to print <.2 MOA at 300, and the 5 shot group <.23 MOA at 300. Even smaller for all of em in the X-ring criteria.

    Primers are an important part of tuning in most all the disciplines on this board, I'm just not so sure the weight sorting will yield the results that I read your striving for.

    Can you say that your tune consistently holds the precision criteria above, and withstands the demands that environmental change, travel, etc put on your system. That would be where I think those top performers are putting there focus. In the tune. And that some barrels are easier to tune smaller than other, is another large factor.

    Hope this helps, even though it doesn't directly answer the question to primer mass.

    The Referenced topics above are from Modern Advancements to Long Range Shooting Volume II, pages 255, and page 88 Table 1.1
     
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  6. JEFFPPC

    JEFFPPC Silver $$ Contributor

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    For me it is very simple. I weigh powder to 1 piece. The weight difference in primers I tested on average Is equal to 5 pieces of powder sometimes 6. So why would I not be critical of my primers?
     
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  7. Rocketvapor

    Rocketvapor

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    I'm all for culling outliers.
    Might have to sort my primers.
    If it does nothing, it surely won't hurt.
    I'll swap a heavy piece of powder for a lighter one :)
     
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  8. dgeesaman

    dgeesaman Gold $$ Contributor

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    That's the first thing I do in any sorting exercise to test for significance.
     
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  9. rsmithsr50

    rsmithsr50

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    gentlemen,
    I was anti primer weighing as there are 4 parts and only 2 are really controlled.
    but we have people that TESTED, AND HAVE shown the weight sorted primers show reduced vertical at 1000.
    I trust these guys, and I weigh my long range primers.
    so it is not perfect, but the numbers are in your favor
     
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  10. 47WillysGuy

    47WillysGuy Gold $$ Contributor

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    Dump the CCI 400's and go with the CCI 450's.
     
  11. SPJ

    SPJ Gold $$ Contributor

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    Any particular reason why
     
  12. Walt Krafft

    Walt Krafft Gold $$ Contributor

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    Many years ago I tested 10 different brands/types of primers. The difference in group size at 100 yards was startling. The primer I was thinking would be the best turned out to be near the worst. CCI's were near the bottom of the results. I would start your testing by comparing different brands/types against each other, and then maybe weigh the best to see if they are consistent.
     
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  13. JEFFPPC

    JEFFPPC Silver $$ Contributor

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    Only problem is conditions, shooter error, etc entering the equation. Would it be better to shoot the two extremes together vs s string of the same from the center lot and measuring the ES of the two strings. I noticed a marked improvement in vertical last year at 1000 with sorted primers but I also was able to better balance my rifle last year for the primers where not the only factor involved.
     
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  14. 47WillysGuy

    47WillysGuy Gold $$ Contributor

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    A year or so ago, there was a discussion about CCI 400 and 450 primers and the gist of the discussion was that the 450 was the primer to go with.

    Reply to SPJ.
     
  15. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    I can explore 450s in the future, but for this upcoming match/this barrel, the 400s are working pretty well. I don't want to go re-work the load with as little time as I have...the barrel has multiple high-x cleans on it at MR distances, so it's not like we're fixing a bad load. Just trying to tighten vertical at 1k.
     
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  16. tom

    tom Gold $$ Contributor

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    Being a person who weighs them, I would get rid of that lot. Extremely bad lots are not that common, but you've managed to find one, as I do use 400s on barrels that prefer them.


    Most important to the vertical is the tune.
    * Does the barrel prefer the 200.20x
    * Does the barrel prefer N150
    * Does it prefer the node it's in vs. Higher/lower
    * Does it prefer cci 400s
    * Does it prefer .0015" interference fit
    * Does it prefer being annealed
    MOST IMPORTANTLY, does it prefer the seating position and powder charge.

    Donovan's suggested test will give you the answer to your question. The key element is the alternating of shots, which turns it into a "ladder" instead of "groups", and this will remove conditions from the test parameters. I still prefer good conditions for such a test, and a rifle capable of 1s.


    Tom

    Edit to add this. With your lot, I would expect to see gains by at least culling those big outliers.
     
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  17. SPJ

    SPJ Gold $$ Contributor

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    I have to agree with your quest for a bit less vertical, always a worthwhile task in my world.
    I found a new front bag that I believe brought me a bit o luck...
    Might have to weigh some primers now.
    Thx for the motivation
    J
     
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  18. dmoran

    dmoran Donovan Moran Silver $$ Contributor

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    In actuality, all aspects to a primer (like you list) would need qualified for every Lot of primers. And since primers that will be used can't be dissected for qualification, I'll just simply spend the 3-hours it takes me to sort/batch/cue a box of 1000. That way I don't have to worry about testing the Lot for inconsistencies, and proceed with the confidence that even if the 3-hours doesn't reap much reward to a Lot like has been proven in bad Lot's, I don't leave anything on the table or hurt accuracy by weight sorting/qualifying all the Lot's that I will use.
     
    Last edited: Mar 4, 2020
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  19. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    It does help, and I just re-read that section so thanks for the cite. :)

    Per my spreadsheet this load is averaging .36 MOA at 300 the 6 times (30 rounds) I've shot it for testing. I'm still inexperienced relative to a lot of guys, but felt like that was good enough to be dangerous in club matches, so just rolled with it.
     
  20. JEFFPPC

    JEFFPPC Silver $$ Contributor

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    At the 2 ranges I shoot 1000 yds at here in Pa all groups are 10 shots not 5. Makes eliminating all possible vertical an ongoing process. Seems to me this along with getting 10 percision shots down range in less than 30 seconds greatly improve your chances for sucess. Only slightly behind the most 2 important elements. Bullets and barrels.
     
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