Over-stabilizing a bullet?

Discussion in 'The Basics, Starting Out' started by LRSickle, Apr 12, 2011.

  1. LRSickle

    LRSickle Well-Known Member

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    I just finished a new build. It's a 6mm Ackley Improved with a 1-8 twist. I originaly wanted to shoot 105s and 107s but the throat is a little short so, thinking that the longer bullets would eat up some case capacity, I tried some 75 Vmax and 75 Sierra HPs. The Sierras flew incredibly well. A guy that has a similar set-up was surprised that I could get a lighter bullet like a 75 to fly so well out of such a tight twist. I know a tighter twist robs a little speed but can you over-stabilize a lighter bullet to where it ruins accuracy??
     
  2. BigSkyGP

    BigSkyGP Well-Known Member

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    I think it will depend a lot on the light bullets construction. Light jacketed varmint bullets may come apart after leaving the barrel from too high of an RPM, due to the tight twist.

    How ever I think if the bullets hold together long enough to hit say a P-dog, could be quite spectacular!

    I don't think it will hurt accuracy enough to worry about.
     

  3. Buffalobob

    Buffalobob Writers Guild

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    The 95 Berger has a very short bearing surface and a high BC and likes a fast twist.

    Jam it to test loads and then ease it back a little.
     
  4. blipelt

    blipelt Well-Known Member

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    I have a unique chance to talk with Richard Schatz quite a little. When visiting with him about fast twist light bullets he mentioned some of his friends were doing it. They turned a pdog into red mist. "They hit like Thor's hammer" he said.

    Brent
     
  5. rscott5028

    rscott5028 Well-Known Member

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    Let's just theorize that you might do a little better with your rifle and 75gr bullets if you had a little slower twist.

    But, it obviously hasn't completely ruined your groups.
     
  6. Boss Hoss

    Boss Hoss Well-Known Member

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    Even if the bullet flies true------if spinning TOO fast will upset excessively at impact causing the bullet to fail. Lead core but the copper I do not know about.
     
  7. squirrelduster

    squirrelduster Well-Known Member

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    My Hart barreled 8 twist 6br was set up for long range squirrel shooting with the 105 and 107's but it shoots the 75 vmax really well and is a grenade when it hits. Seems that ricochets are minimal too.
     
  8. LRSickle

    LRSickle Well-Known Member

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    Maybe my friend's gun with a 1-8.5 twist just didn't like the 75s. I just couldn't imagine him not being able to get the same groups as he can with the 105s he's shooting right now.
     
  9. Forester

    Forester Well-Known Member

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    I think excess twist has more to do with accentuating any flaw/imbalance in the bullet.

    My 8 twist 6BR shoots like a house afire with 80gr Bergers. So well in fact that I have yet to get around to trying the 105s, though I will be soon. I know it does not like 95gr VLDs well at all though.
     
  10. LRSickle

    LRSickle Well-Known Member

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    You might have hit it. A couple days ago I was shooting .14 - .25 groups with some pretty mild loads. As I increased my charges I started to get random fliers. I was trying to find my max velocity. When I backed my charges back down my groups came back together. Maybe my friend is just driving them way too hard.
     
  11. royinidaho

    royinidaho Writers Guild

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    LR,

    I think you're onto the problem. I wonder if an 8 twist is as necessary as advertised.

    I've found that Hornady Interlocks and Nosler Accubonds/Ballistic Tips to be the hardiest jackets. However, in 6 mm they have lousy BCs......

    I've pushed Hornady 140s, Nosler 130s, 140s, 150s to unspeakable velocities out of an 8 twist - 3 groove barrel in 277 without any problems.

    I have duplicated your findings with several other factory and custom bullets.
     
  12. MontanaRifleman

    MontanaRifleman Well-Known Member

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    I'm not an expert on your particular chamber, twist and bullet... but in a conversation with a custom bullet maker with a lot of experience, the issue with "over stabilization" is, at long range your bullet's nose remains oriented "up" and doesn't follow the arc of the bullet path. This is only a concern where deep, reliable and predictable penetration of let's say a large game animal is concerned. In an over stabilization, at long range, the bullet will likely start to tumble on impact.

    As far as accuracy goes, that's anyone's guess, and I really don't think the difference in twist in a 6mm AI is going to matter when penetrating paper or varmints. If you're over speeding a thin jacketed bullet, that's another story.
     
    Last edited: Apr 17, 2011
  13. montana_native

    montana_native Well-Known Member

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    Physics of bullet flight aside, I had the same concern as you but empirical data out of my own gun suggests there is no concern. I've got the 6mm AI with an 8 twist. It shoots the 75 v-max at 3750 with no issues and groups about an inch at 300 yds. Gophers still explode out to 700 yards or so. I've yet to make a hit beyond that distance. Don't be afraid to seat the 105's deep. I'm seating to magazine length (2.820") and getting 3275 fps with Retumbo and very good accuracy.
     
  14. TAC

    TAC Well-Known Member

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    Why not pick up a reamer and set it up the way you want? Your smith should be able to run it down your current barrel chamber and extend the throat. PT&G also sells throat reamers

    You'll always have the reamer and can chamber your next barrel to the same dimensions - it's a good way to go.


    TAC