6BR, throat length for 80 grain bullets

Discussion in '6BR, 6BR Improved & Wildcats' started by knightsniper, Dec 15, 2017.

  1. knightsniper

    knightsniper

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    I am building a 6BR rifle, I want to use berger 80 grain fb varmit bullets, what is the best throat length using these bullets?
     
  2. gunsandgunsmithing

    gunsandgunsmithing The best tuners and wind flags on the market

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    For the 80gr fb bullets, .080-.100" will work very well. The long neck of the BR is pretty forgiving in this regard.
     
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  3. woodbooger

    woodbooger

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    so will .060
     
  4. JamesnTN

    JamesnTN

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    I believe I went with .075
     
  5. boltfluter

    boltfluter

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    .080 works great for me.:D

    Paul
     
  6. mr.big

    mr.big

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    10 twist and faster I would go .104 and 12 twist and slower I would go zero freebore..
     
  7. BartsBullets

    BartsBullets Gold $$ Contributor

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    Big

    I'm curious why you feel the twist rate would require a different freebore for a given bullet?

    Bart
     
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  8. mr.big

    mr.big

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    just that if I am using a 12 or slower twist I will be using bullets that will work very well with a zero freebore and if I am using a 10 or faster that the bullets I would be using would work well with a .104..
     
  9. knightsniper

    knightsniper

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    For all who is concerned ,my
    build is with a 12 twist barrel.
     
  10. Dstroud

    Dstroud

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    For barts 80s fb or bt 80 to 100 will work great on the 80 grain bt the bearing surface at the base of the bullet is over half way down the neck
     
  11. Dstroud

    Dstroud

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    The berger 80 fb have a lot of bearing surface, don't go too short
     
  12. NCVarhtr

    NCVarhtr

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    All zero freebores are not exactly alike. I have a 6X47 Lapua with zero freebore and the base of the 80 Gr Berger fb comes almost (within a few thousands) down to the neck/shoulder (donut) junction. So--based on that reamer configuration, about .040 to .050 would be about right for me. BTW, the 80 Gr Berger is a solid bullet-shoots great and kills extremely well. Good luck..
     
  13. Brett S

    Brett S

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    Here is a 80 gr Berger with a 104 freebore. Be your own judge.
     
  14. Brett S

    Brett S

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    6BR Improved with the same neck length as a BR
     

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  15. hrlincoln

    hrlincoln

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    Looked at your picture and have a couple questions.

    Is your lead angle 1-30-0?
    Where is the 80 with respect to the lands, i.e. .010 off, .010 in or??

    Thanks
     
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  16. urbanrifleman

    urbanrifleman Gold $$ Contributor

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    I am starting to think that .080 thou would work for everything except if you want to shoot 55 grain varmint bullets at the lands. Dave Kiff spec'd my reamer at 125 thou for 108 Bergers and while this works fine it is really way too long for 6Br and is more appropriate for Dasher with the 108. Even with 125 thou I can easily shoot 80s and 70s at the lands, but the bullet is pretty far out there.

    I also think that a 275-276 thou neck would keep the donut from forming on no turn brass. I am really not sure the advantage of these tight necks. They seem to cause more trouble than they fix.
     
  17. Dstroud

    Dstroud

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    The angle is 1-30,the bullet is just at touch making a very small mark when shined with fine steel wool
     
  18. gunsandgunsmithing

    gunsandgunsmithing The best tuners and wind flags on the market

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    The only way a doughnut hurts anything is if you seat bullets at or below it. With all of your scenarios in your post, none should come close to it.

    I agree that about .080-.100 works with a wide aray of bullets in a 6 BR. The long neck makes it very forgiving. I think you hit the nail pretty well on the head. You can shoot 65fb-105 bt bullets in a .100 freebore 6BR, very well.
     

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