6.5mm twist rate

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Long Range, Nov 4, 2012.

  1. Long Range

    Long Range Well-Known Member

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    Looking to build a 6.5 and was wondering what is the best twist rate for the 130-142 grain bullets. I was thinking a 1-8.5 would do but would like to know what everybody's thoughts on this is. The caliber is 6.5 WSM or SAUM leaning more towards the SAUM right now.
     
  2. C.O. Shooter

    C.O. Shooter Well-Known Member

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    How about 1-8 twist?
     

  3. SBruce

    SBruce Well-Known Member

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    8 or 8.5 if you want to shoot 140 VLDs or 142 SMK. 8.5 would probably be fine at the velocities you should be getting with those cases.

    8.5 works good for 140 VLD's at 3000'/sec, 4100' elevation in my 6.5-284. Berger recommends 8 however.?
     
  4. trebark

    trebark Well-Known Member

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    8.5 'should' work. 1:8 will work.
     
  5. Long Range

    Long Range Well-Known Member

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    Thanks guys look like the 8 twist may be the way to go.
     
  6. Hondo64d

    Hondo64d Well-Known Member

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    I have an 8.5 twisted Brux on my .260 and it shoots everything up to and including 140gr VLDs very well. An 8" twist won't hurt, but I'd not fear an 8.5" if that's what you want.

    John
     
  7. Michael Courtney

    Michael Courtney Silver Member

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    The more conservative estimates have you shooting the fastest twist you might possibly need: the longest bullet in the densest air (0 deg F, death valley, etc.).

    The negatives of spinning too fast are small but real: increased spin drift, more barrel resistance engraving and spinning the bullet, possible lower BC due to rifling marks at a larger angle to flight direction, bullet tip lags a bit more aligning with direction of travel, etc.

    Next time I buy a new 6.5 barrel I intend to carefully consider the altitudes and air densities I intend to use it at and buy the slowest twist needed to stabilize my preferred 140 grain match bullets. I can always shoot shorter, lighter bullets if I need to make a trip to lower elevations/higher air densities.

    Just to give you an idea on how much you can get away with at higher elevations. My home range is at about 6400 ft elevation. I can stabilize a 69 grain match bullet from a 1 in 12" twist .223 Remington. I can also stabilize several other bullets that recommend 1 in 9" and 1 in 10" twist rates. At this elevation, a 1 in 10" twist will stabilize the 140 AMAX in 6.5, and a 1 in 9" twist will stabilize the 140 grain Berger VLD.
     
  8. Greyfox

    Greyfox Well-Known Member

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    Berger recommends a 1:8 twist for their 140 VLDs. I have this twist in both my 6.5x284's and it shoots the lighter weight bullets as well ad the 140's.
     
  9. GNERGY

    GNERGY Guest

    I am using an 8 twist in my 6.5 WSM and I am currently testing loads with the 140 Hybrid.
    Tarey
     
  10. SBruce

    SBruce Well-Known Member

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    Where do we find the 140 Hybrid? I haven't seen that on Bergers webpage. Did I just miss it somewhere?

    Nevermind, I found it. Didn't realize it was under the target bullets section, Sorry.
     
  11. Long Range

    Long Range Well-Known Member

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    If you don't mind me asking how long is your barrel and what kind of velocity are you getting from the 6.5 WSM with the 140.

    Thanks
     
  12. trebark

    trebark Well-Known Member

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  13. Capt Academy

    Capt Academy Well-Known Member

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    Please let us know how those 140 Hyb shoot.