Barrel length and twist question

Discussion in 'Long Range Hunting & Shooting' started by Rainy, Apr 15, 2019.


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  1. Gerard Schultz

    Gerard Schultz Well-Known Member

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    Longer barrel = higher speed = more rpms = better terminal performance. Shorter barrel = lower speed = lower rpms = lesser terminal performance.

    The further he shoots, the more Sg he has, using the same load. So, yardage has a telling effect, even if the same load is used.

    One bullet will not do the job at all distances. That is why we need to know at what average distance he shoots and whether he is hunting or target/tactical shooting.

    A 300 Weatherby will not work up the speed to disintegrate a 150gr Accubond, even if the barrel is 28" and the twist is 1:9", it is a moot point.
     
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  2. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    I've had 55 Sierra's blow up in a 8tw 22 Dasher, didnt even make it to the 100 yard target.
     
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  3. Gerard Schultz

    Gerard Schultz Well-Known Member

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    "A 300 Weatherby will not work up the speed to disintegrate a 150gr Accubond, even if the barrel is 28" and the twist is 1:9", it is a moot point."
     
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  4. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    I suggest if all of this confuses the O.P is he gets Brian Litzs book and read it and come to his own conclusion.
     
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  5. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    This is a thread on accurateshooter Bryan Litz was responding to and why I'm a firm believer in not over spinning a bullet more than necessary.
     

    Attached Files:

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  6. Gord0

    Gord0 Well-Known Member

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    Yes, I know this. The OP is talking about faster twist than 10 in his 300wby. I could have went further in my explanation, but you also only took out one tiny portion of my post. I went with a 9 because I want to shoot the 215, and possibly the 180 hammer. Those require at least a 10, but start to get close to marginal at my elevation. I'll get a more consistent BC, and terminal performance with the faster twist. Most modern bullets are much more consistent than bullets if 20yrs ago. They'll generally take more rpm before bad stuff happens. Now if you take a standard 14twist 22-250 that's shooting a 40gr at 4300fps and make it a 7 twist for some 90gr vld's you're probably going to have a problem with the 40's.
     
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  7. LVJ76

    LVJ76 Well-Known Member

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    This is just an opinion, the OP is entitled to use what ever bullet he likes. We may offer some advise but no need to imply he is wrong on what he is doing because he is not, its a personal choice.

    The longer the Barrel the faster the bullet will leave the muzzle since more powder can be burnt when using the appropriate powder. The twist will determine what bullets he can use, a slower twist like a 1 in 12 means he won't be able to use some heavy for caliber bullets like say a 230gr bullet because, it might not be able to stabilize it, but will stabilize a 150gr bullet perfectly. A fastet twist like a 1 in 8" will stabilize the high for caliber bullets but might not stabilize the lighter ones. No, it won't cause a blow up on this caliber, but it might cause some accuracy issues.

    A 1 in 10" is the middle ground and just in case he decides to go with something heavier like a 180gr bullet he will be able to, and also be able to use the 150gr with good results.
     
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  8. Randy Tidwell

    Randy Tidwell Well-Known Member

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    Of course any change to a bullets weight, shape, lenght is going to affect its stability, but I stand by bullet length has allot more affect than weight.

    Example, a 105 grain 6mm VLD bullet (long) needs a much faster twist than a 100 Spitzer.

    Same applies to Copper vs Lead Core, your typical copper 180 grain bullet is much longer than a 180 lead core. The coppers shoot much better with the faster twist. Even being the same weight.

    I have a 257AI that will not stablize a 100 grain Barnes, yet the 25 Souper with a 9 twist bullet does. The 257 AI shoots the 100 grain Balistic tips great. Much shorter bullet.

    So I contend, longer the bullet, the faster it needs to spin. Has very little to do with weight.

    JMHO
     
    Last edited: Apr 18, 2019
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  9. Rainy

    Rainy Member

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    That’s a nice piece of machinery you have there!
     
  10. Rainy

    Rainy Member

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  11. LVJ76

    LVJ76 Well-Known Member

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    The reason why I posted: "Some" high for caliber bullets.

    The larger the bearing surface the faster the twist needs to be.
     
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  12. FEENIX

    FEENIX Well-Known Member

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    The weight and length are directly proportional (reduction in length = reduction in weight, increase in length = increase in weight). In your example, you are restricted (fixed) to 6MM diameter of the bullet so the only way for a bullet increase in weight is an increase in length.

    Below is another example to keep it with the same bullet manufacturer and design (information extracted from Berger), also not sure which 100 spitzer bullet you are referencing ...

    Berger VLD 6MM 95 vs 105.JPG

    SOURCES:
    https://bergerbullets.com/product/6-mm-95-gr-vld-hunting/
    https://bergerbullets.com/product/6-mm-105-gr-vld-hunting/

    To increase the weight from 95 to 105 grain, length has to be increased by .093".

    BTW, I am not disputing that the longer the bullet, the faster the twist requirement for stabilization but you cannot ignore the bullet weight and length relationship that exist.

    Cheers!
     
    Last edited: Apr 19, 2019
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  13. Randy Tidwell

    Randy Tidwell Well-Known Member

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    Feenix, I agree, can't ignore the weight.

    How ever, two bullets of the same diameter and weight that are different lengths will perform better with different twists.


    Compare a 180 grain 30 cal round nose, Spitzer, VLD, for optimum stability you different twist rates.

    The bullet weight is only 10-20% of the equation. Just a guess on the %.

    I understand why everyone relates it to weight, it's easier than keeping track of bullet length.

    I had a long discussion/debate with Barnes at the Shot Show a few years back about this. They finally conceded that their bullets benefited from a faster twist for the same weight lead core bullet.

    JMHO

    PS: OP, sorry we kind of high jacked your post., just order a 10 twist you will be fine.
     
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  14. FEENIX

    FEENIX Well-Known Member

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    Sorry but your 180g round nose, Spitzer, VLD analogy does not make sense. The reason they require different twist for stabilization is because by design they have different lengths and BCs, two essential element of the bullet parameter necessary input to the twist rate calculator. The other two is weight and caliber/bullet diameter. As previously noted, any changes in bullet parameters (BC, caliber/bullet diameter, weight, and length) will have a correlational effect to twist rate/SG relationship.
     
    Last edited: Apr 19, 2019
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