Any Disadvantages to Faster Twist?

Discussion in 'Main Message Board' started by Phil3, Jan 15, 2019.

  1. Phil3

    Phil3

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    I understand sufficient twist is necessary to stabilize a bullet, but are there any negatives associated with a twist rate faster than necessary (other than bullet flying apart)? I recall reading somewhere it is advisable to use the slowest twist possible, but what are downsides to spinning the bullert faster than necessary (other than a possible reduction in muzzle velocity and bullet flying apart)? I have heard the term "over-stabilizing". What is that and why is it (apparently) not good?

    Phil
     
  2. hrlincoln

    hrlincoln Silver $$ Contributor

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    Check out Dan Lilja's website. He has some good write-ups re. twist rates and stabilization.
     
  3. savagedasher

    savagedasher

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    I haven’t seen where over stabbing a bullet is as bad as under stabbing one
     
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  4. 1shot

    1shot Site $$ Sponsor

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    I’ve heard that a to tight of a twist would pressure out quicker, but I have never seen that personally.

    Lloyd
     
  5. ShootDots

    ShootDots Gold $$ Contributor

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    There are some important points to consider. A VERY fast twist, no matter the bullet, will have a significant increase in torque. Depending on how fragile the jacket of the bullet, blow-ups can occur! A fellow I shoot with was shooting a 6.75 twist to stabilize the 90gr VLD out of his .223 F/TR rig. Blow-ups galore! He went to a "straight" 7 twist and the blow-ups ceased. Get a L-O-N-G bearing surfaced bullet, add significant twist and you MAY have uncontrollable torque! I had a 7 Shehane shooting the 180 Scenar. I also had a straight 8 twist to see if I could get the 195s going>>>that was a failure. However, the 180 Scenars shot very well at 2920. Having said that, torque was so bad that my front end would literally come out of the front rest from time to time! Needless to say, I had a very difficult time cleaning a target, even at 600 yards. I simply could not keep the torque under control for over 20 shots.. REMEMBER: I did not need a straight 8 twist for the Scenars. I just happened to have it for the 195s that would not shoot in that barrel..
     
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  6. Hoodoo

    Hoodoo Site $$ Sponsor

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  7. savagedasher

    savagedasher

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    I have a slow twist 22-250 and if I shoot any bullet heavy the a 69 gr they go in the target side way
    The fastest twist I can shoot both
     
  8. JBT

    JBT Gold $$ Contributor

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    Generally, other than increased torque, most won’t notice a difference with the increased twist. Maybe some of the upper echelon BR guys could tell a difference.
     
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  9. spclark

    spclark Gold $$ Contributor

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    Faster twist (than what’s best for a particular bullet’s stability under your shooting conditions) will tend to decrease accuracy when the increase in spin rate makes any manufactured-in bullet variations negatively affect how consistently they behave down-range.

    Think of your bullets as you would tires on your vehicle when they’re not balanced properly: moderate speeds may not show the imbalance but the faster you drive the harder your steering wheel shakes.

    If the bullets you’re using don’t have any variations in center of gravity, faster twists might gain you something. Otherwise excessive twist + velocity will
    tend to make ‘em deflect from an ideal trajectory more.

    There are some folks who believe faster-than-normal twists work OK if loads used don’t push bullets as fast as velocities achievable with typical twist rates. The idea is practical twist + velocity number is a window; exceed one or both & you’re outside it.
     
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  10. msinc

    msinc

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    This!!!!! Yes a fast twist will shoot both light and heavy bullets and it may not blow up the bullets and if all you want to do is send bullets downrange this is the ticket...versatile and practical....if you are just shooting. The problem comes in when you are looking for accuracy. Now, the next thing someone is going to post is how their fast twist rifle shoots everything accurate....yeah, okay...I believe you. Don't get me wrong, I have seen and I own a 1-in-9 223 that does shoot 69 grain bullets as good as it does 55's, but it will not out group my 1-in-14 shooting 50 grain bullets hands down at 100 yards.
    As above and a very good explanation as to why...you always want the slowest twist that will still positively stabilize the bullet you are shooting. The ability to own a rifle that is versatile and practical is one thing, the ability to shoot as accurately as possible is another. I have said it before...if simply twisting a bullet to the max were the answer...barrel makers wouldn't offer but one twist rate, turbo blast!!!
    There are no free lunches...everything is relative. Heavy bullet to get out there with the right twist will not group with light bullets at 100 yards...light bullets with a slow twist wont get out there and group with the heavy stuff. Match bullets and twist to the range you are trying to shoot to. Trying to do both with the same rifle is a compromise that wont quite do either.
     
    Last edited: Jan 15, 2019
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  11. GSPV

    GSPV A failure to plan is a plan for failure.

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    Torque. Jacket separation.
     
  12. Phil3

    Phil3

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    I am glad I erred on the side of slow twists, given the explanations provided. On a 6mmBR barrel I was ordering, I saw so many advocating for the 1:8 barrel, as it could shoot everything, but Berger said my 65 and 68 grain flat based target bullets needed about 1:14 and 1:13 twist respectively. I went with 1:13. At 3,300 fps (estimating velocity will be around that), bullet rpm with an 8 twist barrel would be 297,000. :eek: If 1:13 is sufficient, that is about 183,000 rpm, a heck of a lot slower. Spinning a bullet, even a light one, up to nearly 300,000 rpm in a bit over .001 second could certainly cause some torque in the barrel.

    Phil
     
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  13. Bart B.

    Bart B.

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    The ballistics folks at Frankfort Arsenal chose a 1:12 twist for 7.62 NATO rounds shooting the same weight and length bullets used in 30-06 barrels. In spite of 7.62 velocities being 100 fps slower in their smaller case and shorter barrel.
     
  14. 243winxb

    243winxb

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    Shooting Free recoil in Bench Rest is best with the slowest twist that works. There is less torque that moves the rifle. The 6ppc with a 13-1 twist will work with 65/68 gr bullets for 100/200 yard competition's.

    http://www.bergerbullets.com/twist-rate-calculator/
     
    Last edited: Jan 15, 2019
  15. DirtySteve

    DirtySteve Gold $$ Contributor

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    They answer is yes and no. If you shoot bench rest I would recommend a slower twist over faster. If shooting F-class fast over slower. The reason is in bench rest smallest group wins. The faster the twist the more any minor imbalance in the bullet jacket will be magnified. This will result in a larger group. F-class points win and 1/2 moa is all that is needed. Plus shooting at 1000 yard if the bullet goes sub sonic an over stabilized bullet will not suffer any or at least minimal effects when going through the transonic zone.
     
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  16. Falfan2017

    Falfan2017 Gold $$ Contributor

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    Can the wrong twist rate explain crazy fliers? Like 12” away from an otherwise 3” group at 600?
     
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  17. wedgy

    wedgy Gold $$ Contributor

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    I believe I read something from Litz saying just enough twist to stabilize the bullet was the most accurate.
     
  18. ShootDots

    ShootDots Gold $$ Contributor

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    I suppose that if you have a twist right on the edge of "just enough to work" that might happen. However, I think that when it is THAT far off, there are other factors at work>>>>but it could be that the other factors IN CONJUNCTION with an almost too slow twist could do that..
     
  19. Falfan2017

    Falfan2017 Gold $$ Contributor

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    Wondering because I tried to develop a load for Sierra 110s with a 7.5 twist when 7 is recommended. Showed a lot of potential but had a couple shots that were baffling. Going to do more testing.
     
  20. Ken

    Ken Gold $$ Contributor

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    I have a 22-250 8 twist that will blow up 75 Amaxs. Glad I learned that before I got a suppressor. 80 gr SMKs work fine.
     

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