Big bore twist rate

MileHighShooterMileHighShooter Senior MemberPosts: 4,768 Senior Member
Gettin' ready to order my barrel for the pre-64 project. I've found a few barrel makers that offer both 1:12 and 1:10. The 12 seems to be the world standard for the last 100 years on such matters, but that was also a LONG time before all these fancy new bullets long as a Vista Cruiser. Getting kind of hung up on which one to go with. My plan is going to be mid weight but higher BC/longer mono's and Accubonds.

What do you guys think? Not exactly a long range round, so I won't likely be dropping any of those new SMK's or Bergers in it, but the new 300gr Accubond and the 300gr TSX aren't totally out of the picture. I'd like to play with the 350gr Woodleigh bullets, but those aren't really all that long.
Wambli Ska wrote: »
Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.

Replies

  • knitepoetknitepoet Senior Member Posts: 18,750 Senior Member
    Knowing what "big bore" are you talking about would be a great help
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


  • TeachTeach Senior Member Posts: 18,347 Senior Member
    If you're going with "heavy-for-caliber" bullets, a faster twist rate is a good idea. It's impossible to "over-stabilize" light bullets, but heavy ones need more spin.
    Jerry
    Hide and wail in terror, Eloi- - - -We Morlocks are on the hunt!
    ASK-HOLE Someone who asks for advice and always does something opposite
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    HA! Indeed. Seems I have pulled a snake and made a post about a rifle and failed to mention the most important detail *just a friendly jab Mike*

    375 Ruger
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • ZeeZee Senior Member Posts: 20,564 Senior Member
    375 Ruger

    About time!
    "To Hell with efficiency, it's performance we want!" - Elmer Keith
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    Teach wrote: »
    If you're going with "heavy-for-caliber" bullets, a faster twist rate is a good idea. It's impossible to "over-stabilize" light bullets, but heavy ones need more spin.
    Jerry

    Is most likely up to 300 gr, really heavy for caliber though? Seems like 300gr in 375 is the 180gr in 30 cal :uhm:
    I know I said I'd like to toy with the 350gr Woodleigh but its a rather compact flat base bullet, shorter then several of the 300gr boat tails, so I'm not sure if that really fits in the heavy for caliber arena, due to OAL
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    Zee wrote: »
    About time!

    Hush you, I was recovering from an expensive hunt lol But I got some side work this week, so figured it was a good time! And that project has been at the smith for over a month now and he has detailed written instructions as to how it'll end up.

    ETA - the only thing we haven't fulled covered as of yet (giving him some time to catch up after his hunting rush) is specific brands/prices of the parts. Once I get the barrel down then I have to pick out the bottom metal....that one is giving me a headache currently.
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • knitepoetknitepoet Senior Member Posts: 18,750 Senior Member
    the 1:12 should handle any bullet you want to feed it.

    If the 1:10 was really needed, don't you think there would be more folks making it?
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    knitepoet wrote: »
    the 1:12 should handle any bullet you want to feed it.

    If the 1:10 was really needed, don't you think there would be more folks making it?

    Well that is the conundrum right there, it HAS been working for a long time...but, do you think it would run the chance I can't play with some of the new bullets coming out that are quite long? That 300gr Accubond is HUGE. AB's and TTSX's and such, weren't around even a decade ago.
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • knitepoetknitepoet Senior Member Posts: 18,750 Senior Member
    Well that is the conundrum right there, it HAS been working for a long time...but, do you think it would run the chance I can't play with some of the new bullets coming out that are quite long? That 300gr Accubond is HUGE. AB's and TTSX's and such, weren't around even a decade ago.
    And how many horror stories have you heard about these "new bullets" you've listed tumbling from current rifles? (Most, if not all, of which apparently have a 1:12" twist)
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    knitepoet wrote: »
    And how many horror stories have you heard about these "new bullets" you've listed tumbling from current rifles? (Most, if not all, of which apparently have a 1:12" twist)

    A few with some of the 350gr Barnes and the NF bullets, but that has been from H&H's. Haven't found much of any real data with the faster 375's and these newer bullets
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    Maybe not tumbling, but poor accuracy at least.
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • ZeeZee Senior Member Posts: 20,564 Senior Member
    Call Nosler and ask what twist rate their test barrels are.
    "To Hell with efficiency, it's performance we want!" - Elmer Keith
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    Zee wrote: »
    Call Nosler and ask what twist rate their test barrels are.

    OR I could just look on their site, since I forgot they have detailed load info :bang:
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    Odd....Nosler is using 26" barrel data....no one makes a 26" 375 Ruger. Thought most of the reloading sources were starting to shy away from the much longer then real life barrels. Barnes lists 24" but that is book #4 and doesn't have the TTSX or 350's.
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • ZeeZee Senior Member Posts: 20,564 Senior Member
    What twist?
    "To Hell with efficiency, it's performance we want!" - Elmer Keith
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    1:12 Pac-Nor barrel. Showing most accurate loads in mid range powder charges. Guess that makes the decision easier.

    Another odd thing on their page that REALLY is baffling me....compare the date for the 375 Ruger and the 378 Wby. Not the 375 which is more or less a 375 H&H AI...but the 378, the belted Rigby case. Ruger with top loads is going 2600-2700, 378 is going 2600-2800. And it is using nearly 20 grains more powder in some loads. I thought the 378 was the king of beasts? I mean 3 of the loads are over 100gr, one up to 115gr and that is 2650. Dang, talk about diminishing returns.
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
  • SpkSpk Senior Member Posts: 2,064 Senior Member
    Gettin' ready to order my barrel for the pre-64 project. I've found a few barrel makers that offer both 1:12 and 1:10. The 12 seems to be the world standard for the last 100 years on such matters, but that was also a LONG time before all these fancy new bullets long as a Vista Cruiser. Getting kind of hung up on which one to go with. My plan is going to be mid weight but higher BC/longer mono's and Accubonds.

    What do you guys think? Not exactly a long range round, so I won't likely be dropping any of those new SMK's or Bergers in it, but the new 300gr Accubond and the 300gr TSX aren't totally out of the picture. I'd like to play with the 350gr Woodleigh bullets, but those aren't really all that long.

    My guess is the 1:12 twist will do just fine for what you plan to do. I played with some numbers and came up with this:

    Woodleigh's HS mono .375 cal. 300 grain bullet (1.39 inches) at 2650 fps in a 1:12 twist gives a stability factor of 2.995 or safe stability (less than 1 is unstable, 1-1.25 is a "maybe", depends on conditions, 1.5 is considered gtg for military use and 2 or above is considered safe for nearly all realistic conditions).

    Next, I tried Woodleigh's 350 grain FMJ (1.447") at 2400 fps (guessed at the velocity) and I get a stability factor of 3.013. GTG!

    Finally, I tried Woodleigh's VLD Chey-Tac 350 grain (2.110") at 2400 fps and got a stability factor of 1.005 which I consider "no-go" but using a 1:10 I get a stability factor of 1.447 which is close enough to be used for military work.

    All calculations assume STP (59 degrees F and 29.92 in of Hg)

    You can do the calculations yourself for other bullets here: (you need the bullet length)
    http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

    You can read more about miller stability if you're interested here:
    http://www.jbmballistics.com/ballistics/bibliography/articles/miller_stability_1.pdf
    http://www.jbmballistics.com/ballistics/bibliography/articles/miller_stability_2.pdf

    So unless you plan to use some really long bullets, my guess is that a 1 in 12 will do just fine.

    Is most likely up to 300 gr, really heavy for caliber though? Seems like 300gr in 375 is the 180gr in 30 cal

    I know I said I'd like to toy with the 350gr Woodleigh but its a rather compact flat base bullet, shorter then several of the 300gr boat tails, so I'm not sure if that really fits in the heavy for caliber arena, due to OAL

    Comparing the SDs is an indicator:

    .375 300 grain SD=0.305
    .375 350 grain SD=0.356

    30-06 180 gr. SD=0.271
    30-06 200 gr. SD=0.301
    30-06 220 gr. SD-0.331

    Just my opinion, but that seems pretty good for that caliber.
    1:12 Pac-Nor barrel. Showing most accurate loads in mid range powder charges. Guess that makes the decision easier.

    Another odd thing on their page that REALLY is baffling me....compare the date for the 375 Ruger and the 378 Wby. Not the 375 which is more or less a 375 H&H AI...but the 378, the belted Rigby case. Ruger with top loads is going 2600-2700, 378 is going 2600-2800. And it is using nearly 20 grains more powder in some loads. I thought the 378 was the king of beasts? I mean 3 of the loads are over 100gr, one up to 115gr and that is 2650. Dang, talk about diminishing returns.

    I suspect advances in controlling powder burn characteristics mean we can make more efficient use of cartridge capacity, it's all about getting the best pressure curve for the volume (efficient use of available powder--less waste).

    JMHO
    Hope some of this helps out.
    Beware of false knowledge -- it is often more dangerous than ignorance.
  • MileHighShooterMileHighShooter Senior Member Posts: 4,768 Senior Member
    Dude.....dang. You made my head hurt, in a good way though! I appreciate the extremely thorough break down. I think 12 will be just fine lol. Plus besides the above info, I checked some recoil calculators on the 350's....I think I'll be sticking with 300 as a max and more likely the 250-270's.
    Wambli Ska wrote: »
    Once again, please refrain from cutting short any baseless totally emotional arguments with facts. It leads to boring, completely objective conversations well beyond the comprehension ability of many.
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