Slow twist barrels and high velocity..

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by ol mike, Jan 11, 2007.

  1. ol mike

    ol mike Well-Known Member

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    Howdoo ,

    I know fast twist barrels w/ high bc bullets are where it's at for longrange.------>BUT.

    I am a coyote hunter and a gun that shoots like a laserbeam is a good thing.
    When calling predators in open country shots are rarely over 350 yds. so a lighter bullet will shoot flatter within these ranges.--So.

    When i rebarrel my 25-06 i'm thinking of going w/a 27" 25-06 AI w/a 1-12 ? 13-14" twist ?
    It will be geared to shoot an 85gr nos.bt. at 4000 fps.
    It should flatten coyotes and rockchucks out to 500 yds..

    I know many of you have called coyotes or hunted game where there is no time to range -dial elevation etc-etc- it's put crosshair on fur and pull trigger.
    So what do you'all think about this idea ?? -Mike
     
  2. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Ol'Mike,

    You may come close to 4K with an 85 gr pill in a 25-06 AI but I would say you would be pushing it pretty darn hard. In most of the 257 Wby rifles I have tested they were hard pressed to puch much over 3800-3850 fps with the 85 gr pills and if you look in most loading manuals they will list the Wby at 3750-3800 fps tops for this bullet weight.

    What receiver are you using for the platform of this rifle?

    If its a Rem 700, why not look at a 257 STW. If your wanting an 85 gr pill at 4000 fps I suspect you care very little for pelt damage.

    You can get a legit 3800-3850 fps in a 27" barrel but with a 100 gr Ballistic Tip instead of an 85 gr pill.

    I am currently playing with a personal rifle I chambered in my 257 AX. THis round has exactly 2 grains more capacity then the STW but in a case no longer then the 25-06.

    I am testing it with 156 gr ULD RBBTs right now but will be seeing what the 100 gr pills will do in it as well. It has a 27" Lilja.

    I guess my thinking is if you are not concerned with pelt damage, why limit yourself to the 25-06 AI. Not that it is not a great round, it certainly is, but you sound like you want as flat as possible out to 350 yards or so, there are much more impressive rounds for such work in the same caliber.

    back to your question on twist rate. It will suprise you how little difference there would be in a 1-10 and 1-14 twist barrel as far as velocity results in a chambering like the 25-06 AI. I would say far less then 50 fps. I would much rather have the ability to use a wider range of bullets if wanted then only be able to shoot the lightweight pills.

    Your theory is correct though, out to 350 yards or so, velocity, if high enough will outperform BC, but you need alot of velocity. Winddrift to that range will be a toss up.

    Kirby Allen(50)
     

  3. ol mike

    ol mike Well-Known Member

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    Thanks for the imput Kirby.

    I just kind of threw 4000 fps out there to show my mindset.

    I really like the low recoil level of the 25-06 but the 257 stw w/a 100 gr bt doing 3800 fps does sound good /ubbthreads/images/graemlins/smile.gif!

    Also i would have thought a slower twist would have led to more velocity -that's good to know that a 1-12 -13 twist would moreless be a waste.
    Thanks -Mike
     
  4. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    I talked with Dan Lilja about the difference on velocity comparing a stadnard twist(1-10) to a fast twist(1-7) when I was starting my 7mm AM project. He said the difference from the rifling twist would be insignificant and that barrel to barrel variations would make more of a difference then the change in twist rate.

    I tend to trust Dan when it comes to topics about internal ballistics, he has not steared me wrong yet.

    One thing to keep in mind however is that if you want to use the thin jacketed bullets at very high velocity, the slower twist really become important because the reduce RPM levels to the point where the thin jacketed bullets can survive the high launch speeds.

    For this reason they certainly do have their merit.

    Kirby Allen(50)
     
  5. Dzaw

    Dzaw Well-Known Member

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    Can you say 243 Hawk?
     
  6. Guest

    Guest Guest

    I have an old friend that built a 22-250 AI with a 16 twist and it stabilizid the heavy bullets,probably because of the extra velocity.I shoot a 10 twist 25-06 26" 75gr vmax at 3900fps using H414.Also a 115 Berger vld@ 3200 using VHT N165.An Improved 25-06 should do even better with the slight increase in capacity and slow powder.I have found that N165 is a lot slower than VHT manuals indicate.
    OLD BEAR
     
  7. killahog

    killahog Well-Known Member

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    Old bear Have you actually shot the 25-06 over a chrony or are you using an estimation for the velocity?. I have a 25-06 AI and I am going to try some 75g vmax next week however I have talked to 2 others who have had those bullets blow up before reaching the target at velocity above 3800 fps. I have also used the 115 berger vld's and Hit a prairie dog @ 1100 yards But the little rat made it to its hole and I could not confirm it was killed. I now for a fact though I hit it and I also had a witness that saw it. Just for the record it took me 21 shots to hit him. I have also talked to Dan about the rate of twist vs velocity and I believe the biggest factor is not variance of barrel's but it would be the bearing surface of the bullet, 75g bullet as opposed to a 100g bullet one would speculate a 25% decrease in friction although I am not sure how much more friction would be added by a slower twist.
     
  8. YOTES2CALL

    YOTES2CALL Well-Known Member

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    Killahog.... PM sent

    thanks
     
  9. Sendero_Man

    Sendero_Man <strong>SPONSOR</strong>

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    Killahog,

    I'd like to try a faster twist barrel in my Swift.... do you like the 75 grain ? Or when you try them, let me know please.

    I am thinking of rebarreling my Swift to a 1 in 8 for the heavier bullets and handle the wind here better....

    thanks,
    SM
     
  10. Centre Punch

    Centre Punch Well-Known Member

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  11. Sendero_Man

    Sendero_Man <strong>SPONSOR</strong>

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    Killahog....

    U around ??
     
  12. Sendero_Man

    Sendero_Man <strong>SPONSOR</strong>

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    killahog.... where u at man ??
     
  13. Sendero_Man

    Sendero_Man <strong>SPONSOR</strong>

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    BTT
     
  14. BountyHunter

    BountyHunter Writers Guild

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    Go to 6mmbr.com and look for Richards stocks and gunsmithing. He is building exactly the type gun you are talking about. He is shooting LR ground hogs using a 6mm Rem AI with 75/87 gr around 3800 I think. He is also using a 300 WSM with 125 Btips at around 4000. He is definetly using the slower twist barrels to reduce RPM and bullet blowups associated with fast twist.

    You have the LR BR guys going to 12 and 13 twists in the 300 WSM and 300 Ack shooting 187 BIBs.

    BH