Barrel rate of twist

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Methow Packer, Apr 26, 2014.

  1. Methow Packer

    Methow Packer Well-Known Member

    Messages:
    112
    Joined:
    Apr 14, 2013
    When a bullet manufacture states the rate of twist for a bullet ,example 1-12 twist or better for 185 VLD are they saying that 1-12 is optimum for that bullet and anything faster will work?

    I recognize some bullets do better at a faster RPM than others but are they really saying 1-12 is the best for that bullet?
     
  2. Barrelnut

    Barrelnut Well-Known Member

    Messages:
    2,394
    Joined:
    Dec 16, 2013
    They are pretty much saying that is the slowest twist that will stabilize the bullet. Not the optimum.

    Below link is to the Berger twist calculator. It is pretty informative. Plug in some numbers and see what you get.

    http://www.bergerbullets.com/litz/TwistRuleAltWP.php
     

  3. Methow Packer

    Methow Packer Well-Known Member

    Messages:
    112
    Joined:
    Apr 14, 2013
    Thanks. Just got my .300 WM back from rebarreling and discovered they installed a 12 twist. Not sure how that will work out. I want to use 185 and 190 VLD and some 215. Wonder if I'll have to start over cause it should probably have been 10 or 11 at best. At this point all I can do is break it in and try it out for a while.
     
  4. Barrelnut

    Barrelnut Well-Known Member

    Messages:
    2,394
    Joined:
    Dec 16, 2013
    On the bright side, it will probably give you some good speeds with lighter bullets.
     
  5. Gerard Schultz

    Gerard Schultz Official LRH Sponsor

    Messages:
    127
    Joined:
    May 9, 2001
    The spec for a 300WM is 1:10" twist. A 12" twist turns it into a paper and steel rifle and it is not a hunter unless you limit the distance by using shorter bullets.

    The twist calculator on the Berger page works very well with jacketed lead core bullets. It does not do well with turned copper bullets. For turned copper, use this calculator which works with any type of bullet construction.

    NPS Home
     
  6. Michael Eichele

    Michael Eichele Well-Known Member

    Messages:
    3,829
    Joined:
    Jan 6, 2003
    Fortunately, the 12x works very well with 185-200 grain bullets. 215 no but up to 200 yes. And as GS pointed out, only in regards to jacketed lead and not solid copper.
     
  7. Gerard Schultz

    Gerard Schultz Official LRH Sponsor

    Messages:
    127
    Joined:
    May 9, 2001
  8. Michael Eichele

    Michael Eichele Well-Known Member

    Messages:
    3,829
    Joined:
    Jan 6, 2003
    Having the ability to shoot at sea level and sub zero (F.) temps, I'd say Berger is pretty accurate. I believe they use the Miller formula? Not 100% sure. I have yet to see a 200 grain pill not reach 1k without punching perfect holes with good accuracy from 12x barrels. Of course Berger's 200 grain hybrid maybe different but others do just fine.
     
  9. FearNoWind

    FearNoWind Well-Known Member

    Messages:
    2,314
    Joined:
    Jul 10, 2012
    You're probably limited to 185 grain and lighter. Heavier bullets are likely to be ballistically unstable at 1:12. But unless you're hunting elephants, bullets in that renage should be enough for anything on the North American Continent. gun)
     
  10. Chickenthief

    Chickenthief Member

    Messages:
    6
    Joined:
    Aug 4, 2011
  11. Gerard Schultz

    Gerard Schultz Official LRH Sponsor

    Messages:
    127
    Joined:
    May 9, 2001
    That is a Miller calculation and is limited to jacketed lead bullets.
     
  12. Michael Eichele

    Michael Eichele Well-Known Member

    Messages:
    3,829
    Joined:
    Jan 6, 2003
    The bullets that this thread is based on are jacketed lead. The miller formula works exceptionally well with jacketed lead bullets.
     
  13. Gerard Schultz

    Gerard Schultz Official LRH Sponsor

    Messages:
    127
    Joined:
    May 9, 2001
    That is not stated anywhere, least of all by the original post. Given that the thread will be read by users of copper monos as well, it must be stressed that the Miller Formula does not do well with copper mono bullets. It also gives a margin of error with certain types of jacketed lead bullets but it is easy to use. That is the attraction and the temptation - ease of use.

    As with most things, easy is not always right and it needs pointing out.

    A good example is the easy way to calculate SD: Bullet diameter squared, divided by bullet weight is easy, but it is not right, is it?
     
  14. Michael Eichele

    Michael Eichele Well-Known Member

    Messages:
    3,829
    Joined:
    Jan 6, 2003
    GS,

    Below is post number 3 from this thread. Posted by the thread starter. Unless I'm mistaken, the 185 and 190 VLDs are jacketed lead.

    Sorry!

    My point here is not to argue with you. The point here is that the original poster had questions as to whether or not he could use 185, 190 and 215 grain VLDs, (which are jacketed lead) in a 12x barrel. Miller says yes to the 185 and 190. That fact that miller doesn't work perfectly with monos is not really relevant to this particular thread.