28" Dasher barrel Contour? HV or Straight

Discussion in '6BR, 6BR Improved & Wildcats' started by chadwickz71, Aug 21, 2017.

  1. Gabe22BR

    Gabe22BR Gold $$ Contributor

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    Altitude plays a role in factoring twist rates.
     
  2. JBT

    JBT Gold $$ Contributor

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    It certainly does
     
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  3. 4xforfun

    4xforfun Gold $$ Contributor

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    Fine .....what would the altitude have to be to make a 55 grain Nosler ballistic tip show stable in 1 and 14 twist Barrel and then get back to me.
     
  4. Gabe22BR

    Gabe22BR Gold $$ Contributor

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    1-12 here
     
  5. BenPerfected

    BenPerfected Silver $$ Contributor

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    Are there any altitude/twist rate charts that show the impact on accuracy? I can see the need for the normal adjustment of the powder charge or a barrel tuner.
    Ben
     
  6. kvd

    kvd Silver $$ Contributor

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    As does humidity.

    One of the problems with asking "what twist rate works the best" for a given bullet on a worldwide forum is that the responses are not quantified. In other words, what works great for a guy in arid Arizona may not be optimum for a guy shooting the same bullet in Florida.

    I tend to agree with 4Xforfun that with custom barrels, we tend to go with ever increasing twist rates in order to achieve high SG numbers. This is partly due to the fact that bullet weights and lengths seem to be always increasing. Thus the requirement for faster twist rates for optimum bullet stability. At least we're not into turns in fractions of an inch - yet!

    Chapter 1 in Volume I of Bryan Litz's book Modern Advancements In Long Range Shooting dispels the myth that fast twist rates reduce muzzle velocity to a significant degree. Given that, the prevailing philosophy seems to be “the faster the twist the better” – as long as the bullet doesn’t fly apart.

    My 2¢ worth.

    Ken
     
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  7. 4xforfun

    4xforfun Gold $$ Contributor

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    I didn't ask what twist rate...I asked at what altitude does a 1-14 twist become stable with the 55 NBT (length of .815).
     
  8. Gabe22BR

    Gabe22BR Gold $$ Contributor

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    well Tod, here @ 350' above sea level, a .224 55gr Nolser, will keyhole @ 100 yds. , with a 222 rifle.
     
  9. 4xforfun

    4xforfun Gold $$ Contributor

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    Again...maybe yes..maybe no. We must have 10,000 55 nbt's down range here at 900 feet ASL that shot perfect in 14 twist tubes. Then one day we had a new 22-250 AI that put them straight sideways at 25 yards. I was confused so I ran them in the Berger Twist Calculator. .75ish.

    We were obviously doing it wrong all those years, and finally got it right when they started to keyhole!! ;)

    Like I said.....run the 215 hybrid at 3000 with an 11 and run a 200 hybrid at 2900 in a 12 twist. Both come in at around 1.2. Both shoot VERY SMALL at 1000 yards in COMP.

    Like I said...you can't live your life based on what the Berger calc says.

    Just sayin..
    Tod
     
  10. Gabe22BR

    Gabe22BR Gold $$ Contributor

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    Agree to disagree
    It gives you a place to start;) Depending on your location, and places to shoot. one must fine tune for the conditions

    maybe yes...maybe no.--- I opt for the faster & HV contour for making weight.
    Just don't add too much weight to the stock
     
  11. 4xforfun

    4xforfun Gold $$ Contributor

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    I agree...if I am building xyz and plan on shooting abc bullet I would cirtianly take a look at the calculator. I didn't plan on shooting the 215 in the 11 twist as it didn't exist, but tried it !! Same with the 200 Hybrid and the 12 twist...my plan was to shoot the 187 BIB flat base. It didn't shoot for crap. Tried the 200 HB and instant winner!!
     
  12. JBT

    JBT Gold $$ Contributor

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    I shot 215's just fine out of a .300 Win Mag 11" twist...I do use 10" twists now and have a 9" twist ready to be chambered.
     
  13. 4xforfun

    4xforfun Gold $$ Contributor

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    Yep...I've got 10's, 11's, and 12's in both 300 WSM and WBY. We will see if the new "heavy weight" 30 cal comes out...may need to look at a 9.5 or 9.0 twist.
     

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