Distance to the lands

Discussion in 'Main Message Board' started by RetiredArmy, Oct 1, 2019.

  1. RetiredArmy

    RetiredArmy Silver $$ Contributor

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    How often do most of you check this measurement after your initial load development? Let's just say (example only) your at touch at say, 1.265 cbto your new measurement is 1.285 cbto. How do you go about adjusting your load, And how often is this done.
    Thanks Bill
     
  2. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Watch your velocity
     
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  3. ShootDots

    ShootDots Gold $$ Contributor

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    Let's say I load for a match and my 200-20Xs are set at 18 thousandths OFF the lands. After a 3 x 20 match PLUS sighters, the same bullet is now 22 thousandths OFF the lands, I adjust NOT for how much powder to put in BUT to get the 200-20Xs back to 18 off!
     
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  4. RetiredArmy

    RetiredArmy Silver $$ Contributor

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    So I seat bullet longer so I'm back at 18 off. Will I not have to adjust powder as well? As y'all can tell, I'm confused.
    Thanks Bill
     
  5. Cigarcop

    Cigarcop Gold $$ Contributor

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    I don’t adjust my powder charge till I’m about 1k rds on it then I might go up a tenth or two.... but I chase the lands all the way.
     
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  6. spaniel

    spaniel

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    Distance to lands is what matters. Itty bitty difference in case capacity does not meaningfully affect charge weight within reason. How often I re-check my distance to lands depends on how hot a round I am shooting. I check my 243AI a lot more than a 223, for example.
     
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  7. BartsBullets

    BartsBullets Gold $$ Contributor

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    Hey Bill,

    The only way you can know, is to test it. I’ve had some barrels that I had to chase the lands and others that I haven’t. It’s just part of the pre-match routine. Go out and shoot it where its at then move it in a couple of thousands at a time and see if it helps. If you don’t test it you’re just guessing. Same thing with powder.

    Bart
     
    Last edited: Oct 1, 2019
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  8. ShootDots

    ShootDots Gold $$ Contributor

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    Take a look at what 4 thousandths looks like on a set of calipers. Changing powder charges for the tiniest of case capacity change would be so minuscule as to be virtually unnoticeable! So changing powder charges would be almost impossible to keep the exact same velocity. However, a 4 thousandths change in seating depth could yield vastly different results..
     
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  9. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Tune is constantly changing. Most barrels will need you to routinely test to stay at their peak. My preference is to chase the lands and tune with powder, until that doesn't cut it, then you have to revisit your seating. But thats just me because most of the barrels I have owned did want you to chase the lands, but not all of them.
     
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  10. mikecr

    mikecr

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    I find best CBTO off the lands (OTL), and I never change it for the accurate life of the barrel.
    Have never had to.

    I believe land relationship matters less & less with a retreating throat -while OTL anyway.
    Those relying on ITL settings, that's different. I wouldn't bother with that.
     
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  11. BartsBullets

    BartsBullets Gold $$ Contributor

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    Just finished checking seating depth on the gun I intend to shoot at the Nationals! No change required. Moved the seating depth in and it started pitching shots.

    Bart
     
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  12. RetiredArmy

    RetiredArmy Silver $$ Contributor

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    Bart, when you say you checked seating depth, do you mean you rechecked the distance to the lands of your known good load?
    Thanks Bill
     
  13. kvd

    kvd Silver $$ Contributor

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    Interesting. If you're the type of person that weighs cases in order to possibly gain some idea of case volume - and sorts cases based on this information - then it would suggest that seating depth is more about micro adjusting case volume than distance from the lands to the bearing surface. On the other hand, it could mean you're in a sweet spot in terms of seating depth and a few thousandths of throat erosion isn't going to materially change anything at the target.

    Who can really say?
     
  14. SPJ

    SPJ Gold $$ Contributor

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  15. BartsBullets

    BartsBullets Gold $$ Contributor

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    The Target!
     
  16. SPJ

    SPJ Gold $$ Contributor

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    Yes Sir” the target. tells all !!!
     
  17. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Quit talking crazy. We work up loads on the computer and chronograph only around here
     
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  18. BartsBullets

    BartsBullets Gold $$ Contributor

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    Bill,

    With a new barrel I’ll figure out where touch is and start looking for what I believe to be the correct seating depth. For me that’s usually.006 to .010 into the lands. Once I have that I don’t about care about “the relationship between the lands and bullet any more” because its no longer relevant. From that point forward I’ll take the gun out and shoot the old seating depth against new seating depths going further in. The barrel will tell me what it wants. Today it said leave me right where I’m at.
    B8B02CE1-2224-482B-8758-145925352779.jpeg

    Now I speculate that I get away not having to change my seating depth as much as someone who is jumping the bullet. Because of the lands eroding getting further away from the bullet. While I’m still in the rifling.

    Bart
     
    Last edited: Oct 2, 2019
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  19. RetiredArmy

    RetiredArmy Silver $$ Contributor

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    Bart,
    Thank you for responding. It's starting to make a little more sence. I feel more comfortable jumping my bullets then jamming them. Even if it's only 4 or 5 thousands. So I'm assuming when my load (groups ) start going south it's time to remeasure?
    Again thank you
    Bill
     
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  20. SPJ

    SPJ Gold $$ Contributor

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    And then ask what went wrong
     

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