Here is my tip on how to find ideal seating depth.

Discussion in 'Main Message Board' started by jamesdmock, Aug 30, 2017.

  1. jamesdmock

    jamesdmock Gold $$ Contributor

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    To find the ideal seating depth for a given powder and bullet a person needs to first find the jam for that bullet. Also, one needs to load at three different powder charges for each of the following seating depths. These should be a mild charge, a moderate one, and a hot load. These three loads are tested at different seating depths...starting at jam and then moving away from jam in .005 inch increments. (see picture below).

    When one finds a 3-shot group that is in the same relative position with each powder charge (like those at .015 off), that is a great seating depth. After using this to find the best depth, one can tweak his best load by trying within the .005 inch window or within the .5 grain powder charge. Good shooting....James Mock
    DSCF2002 (1).JPG
     
  2. sparker

    sparker

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    Fascinating!
     
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  3. nmkid

    nmkid Gold $$ Contributor

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    Very interesting!!
     
  4. Grimstod

    Grimstod Machinist, Designer, and Shooter. Gold $$ Contributor

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    Good technique. I would add one thing. When shooting a group if I shot two and they were already a large group I would not bother shooting the third. Saves your barrel some.
     
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  5. wholman

    wholman

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  6. dmoran

    dmoran Gold $$ Contributor

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    @jamesdmock -
    Good post...thanks for sharing !.!.!
    Question: since the word "jam" gets used so loosely, could you explain your "jam" and how it compares to "hard jam", "zero", and/or "In/Off".
    Donovan
     
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  7. jamesdmock

    jamesdmock Gold $$ Contributor

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    Jam to me is just a starting point. I find jam by closing the bolt on a long seated bullet that is pushed back by the lands. I do this with light neck tension (about .001).
     
  8. dmoran

    dmoran Gold $$ Contributor

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    Thanks..... that was my guess, and is what I know a light "jam" length to be as well.
     
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  9. MrBottleneck

    MrBottleneck Silver $$ Contributor

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  10. 500Stroker

    500Stroker Silver $$ Contributor

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    You are looking at over sixty rounds to complete your method, how often did you clean the barrel during the testing?
    Did you shot the test all with a hot barrel or did you allow for cool down.
    Keep up the good work.
     
    Last edited: Aug 30, 2017
  11. Rushty

    Rushty Gold $$ Contributor

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    Thanks for the great info, that's a very interesting way to tune.

    Cheers Rushty
     
  12. RampedRaptor

    RampedRaptor Silver $$ Contributor

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    Interesting. However, looking at the target it appears only 15 thou jump is acceptable. Does one chase the lands after a optimal charge weight has been identified?
     
  13. ben lurkin

    ben lurkin Silver $$ Contributor

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    Given your results, it appears the same could be accomplished with 1 each of the light, medium, and hot load. That being the case, you could just shoot each series and go with the smallest group.

    Thoughts?
     
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  14. dsculley

    dsculley

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    Good method in general but it does not cover enough distance. If I used that for Berger bullets in my rifles I would not have found my best seating depth. Your method stops at 0.030 off. In my 7mm RM my best depth with Berger hunting bullets is 0.070 off. My 6.5x47 likes .060 off with 140 gr Berger target bullets. I use the Berger seating depth test first, then test the area that shows promise with smaller increments. I am not dogging your method, sounds solid, just that sometimes you need to test a wider range than you have presented. I think that next time I will use the Berger test to find the best area to test, then use this for fine tuning and see how it works out. I like the part about testing with multiple loads. I am sure that will find the optimal seating depth that works independent of powder charge.

    BTW, the contrast between 0.015 off and those above and below are dramatic in that example.

    One more tool to tuck away for future use, thanks for sharing.
     
  15. jsthntn247

    jsthntn247 Silver $$ Contributor

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    Interesting. Looking at the targets, seems like you could take .010 off and tweak a few tenths powder either side of the medium powder charge and have a good load that would stay consistent through conditions. Looks like 8-15 thou off is the preferred seating depth.
     
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  16. msinc

    msinc

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    Not knocking your method by no means, and thanks a million for posting...I am always ready to learn something, but how is this different from the way Berger has said previously to find seating depth for their "VLD Hunting" bullets???? Start at bullet touching lands and load several test rounds each of cartridges at .010" deeper seated bullets then shoot them all and find the best group and work on it from there was my basic understanding. They say "one group of cartridges will group better than the others" and that is exactly what I found to be true.
    Again, not trying to be facetious, but this reads as if you "discovered" something new when it is extremely very similar to what the rest of the world has been doing with Berger bullets among others. Just asking if I am missing some significant difference???? Again, thanks for posting.
     
  17. jamesdmock

    jamesdmock Gold $$ Contributor

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    As many have said, "There is really nothing new in the world." The ideas for the method outlined above came from three sources. I interviewed all three for PS and got their ideas and assimilated them into one idea. These three were Tony Boyer, Joe Krupa, and Jack Neary (all three are Hall of Fame Members). Later, I was told by Eric Stecker (president of Berger) to not be afraid to jump VLD bullets quite a bit (as in .040 or more). I can usually find a good load without that much jump. Tony Boyer does not start at jam, but at "just touching" and always moves into the lands. He told me that he doesn't trust jumping with short range BR bullets. Gary Ocock told me that he has used the same method for many years....that is, he always shoots BT bullets and he normally jumps them by seating the bullets .030" off of jam and tunes with powder charge. So my method outlined above is a guide for those seeking a method for tuning. Sometimes I shorten the method by starting with bullets at .005 off jam because I have not had luck with bullets at jam. Also, I may shorten the process by using only two powder charges ... mild and hot. Good shooting...James
     
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  18. msinc

    msinc

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    Now I get it...it's your opening title that is confusing to me..."Here's MY tip...."
     
  19. CharlieNC

    CharlieNC Silver $$ Contributor

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    James you mentioned you were looking for most stable POI, not group size. In this example the smallest groups also occurred at most stable POI; has this typically been your experience for other similar evaluations? I would assume so since that is probably your ultimate goal?
     
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  20. Rsadams

    Rsadams

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    Nice... Thanks for posting..
     

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