260 nodes and velocity

Discussion in 'Long Range Hunting & Shooting' started by Jdgar, Apr 18, 2019.


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  1. Jdgar

    Jdgar New Member

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    Apr 18, 2019
    Hoping someone might have some experience with this. I’m shooting 260 142 mk moly with rem brass h4831sc had good results around 2800 fps. They’ve discontinued these bullets Formed some brass from lc lr 308 brass. Having to switch to regular 142 mk. I have reduced powder charge 2 grains. Getting a 5” higher poi and a bigger group at 600 yds. Assuming higher velocity. Could a person expect a noncoated bullet to shoot as well as a moly at the same velocity or need to look elsewhere Can get higher velocity with h4350 but h4831 is more accurate
     
  2. jtmpilot

    jtmpilot Active Member

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    I was just out shooting my 260 today. It is a F class rifle so the barrel is fairly long,,,,28 inches. I was shooting 139 Lapua Scenars over 47.0 grains of 4831 SC. velocity was averaging right a 2910 FPS according to Labradar. The freebore is longer than SAAMI spec and the bullets are seated fairly long...
     
  3. BallisticsGuy

    BallisticsGuy Well-Known Member

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    Sierra still makes 142MK's. Moly coating vs. naked bullets should be generally irrelevant to accuracy. It may happen that your rifle treats one differently to another but there's no inherent reason why it should.

    Why you reduced your load so aggressively is a question spinning around my head. Did you not work back up for some particular reason?

    You know you can get a moly kit and moly coat at home in a tumbler. Kits are stupid cheap.
     
  4. Jdgar

    Jdgar New Member

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    I formed 1000+ brass from lc lr 308 It has about 1 - 1 1/2 grains less capacity is one reason. I reduced .5 grain with the same rem brass and plain 142 mk. Didn’t have a lot of rem brass so trying to find a load with other brass. Don’t have a chronograph Guessing velocity by drop from 600 to 1000 yds. wondering if I could expect other bullets to have a node around 2800 FPS Or if each type of bullet had its own node velocity.
    And far apart nodes could be expected.
    26” Varmint if that matters
     
  5. Jdgar

    Jdgar New Member

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    Have you had any experience shooting the same bullet moly coated and plain.
     
  6. BallisticsGuy

    BallisticsGuy Well-Known Member

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    1. Get a chronograph and stop guessing.
    2. Bullets don't have nodes, barrels do. The "node" is an amplitude crest or valley in the vibration of the barrel.
    3. Changing brass means you've completely changed your load and need to re-develop.
    4. Changing powder charge means you've completely changed your load and need to re-develop.
    5. Changing from moly coated to uncoated means you've changed your load and need to re-develop (this does not apply in my experience with HBN coating, bare or coated with Boron Nitride doesn't seem to matter in my extensive testing).

    You see where I'm going with this right? If you were not expecting changes in POI and MV then your expectations were not in line with what actually happens in our universe.
     
  7. Jdgar

    Jdgar New Member

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    Thanks for your input
    Certainly agree on chronograph. I’ve been looking Any suggestions on one.

    So if I’m understanding you right. Even shooting the same brass bullets primers. But Different powders shooting the same velocity would cause the barrel to vibrate differently ?
     
  8. BallisticsGuy

    BallisticsGuy Well-Known Member

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    yes
     
  9. Jason millichamp

    Jason millichamp New Member

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    Hi
    My friend and I shoot tikka .260s. Both rifles had load development separately and both rifles are very accurate using 44.4 grns of adi 2209 or h4350 which is made by adi. Shooting lapua scenar 139 grn with br2 primers. They go at 2830 fps which is what we both settled on separately. Which is about max load which is what the tikkas seem to like.
     
  10. aushunter1

    aushunter1 Well-Known Member

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    Yes any change you make has an effect on the harmonics of the barrel.
    If you still want to use a coating projectile why don't you buy a coating kit & do them yourself?
    You would still need to redo your load development again as they will stillbe different to the bought ones.
    You have plenty of options on crony's over there & they are way cheaper than here.
    I would go either the Labradar or the Steinert, I have a Magneto speed which attaches to the barrel & will affect the groupings slightly.
     
  11. epoletna

    epoletna Well-Known Member

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    You asked for a recommendation for a chronograph. Labradar. It works without being attached to the barrel and without you having to shoot right over the sensors. (Ask owners of chronographs you shoot over how many have inadvertently shot their chronograph. Some more than once. . .)
     
    silvertip2 and Michael Souther like this.
  12. BallisticsGuy

    BallisticsGuy Well-Known Member

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    I'd go magnetospeed myself. It changes POI, not usually group size. POI changes are as consistent as your mounting of the bayo unit and it doesn't cost 600 dollars.
     
  13. Michael Souther

    Michael Souther Well-Known Member

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    Labradar because it does not attach to the barrel and dependable does not depend on light. I went with Berger and Hornady ELDs . I do like the 260 rem and Rem Hunter rifle. I am still trying different brass and several powders 760 Winchester for one. look in the Berger manual and Hornady 10 manual
     
  14. RYEWSKY25284

    RYEWSKY25284 Active Member

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    I shoot nothing but moly. Going back to a non-moly bullet will leave some copper "spotting" in the barrel. This "CAN" leave you with some accuracy gremlin's. The fellow who built my rifles was a famed bench rest shooter. And he advised me that once you start moly coating you can't go back and forth between coated-non-coated. And, said in fact, that it will have a negative affect accuracy.
     
    Frog4aday likes this.