1 in 12 in 308

Discussion in 'Long Range Hunting & Shooting' started by avfromvt, Aug 12, 2011.

  1. avfromvt

    avfromvt Member

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    Just getting my first long range rig I really want to start with a factory rifle. I settled on the CZ 550 varmint in 308. The barrel twist rate is 1 in 12, the standard seems to be more like 1 in 10. I will be shooting factory ammo probably 168 or 178. Is there any disadvantages to the faster twist rate. This will be a deer rifle for out to 500-600 yards.
     
    Last edited: Aug 12, 2011
  2. blipelt

    blipelt Well-Known Member

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    A slower twist like the 1:12 might not stabilize a heavier bullet. Don't have much experience with the 308 yet just picked one up yesterday. Cooper classic weighs only 7.5lbs with 4.5-14 CDS on top. Mine has the 1:10 and from the group and load from the factory they shot was one hole group with 168smk. I would try and find a 1:10 if it was me.

    Brent
     

  3. hatfield954

    hatfield954 Well-Known Member

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    I can't think of a disadvantage of having a faster twist rate right at this moment. I found out a faster twist rate requires a heavier grain bullet to stabilize better for accuracy. A 1 in 12 twist rate is slow and should stabilize better with a lighter grain bullet, like 150's. You can find factory ammo even lighter than that if you just had to. I don't know what the terminal ballistics would be like at that range with a bullet lighter than a 150. I had a remington .270 and had to use the heaviest grain bullet i could find to get it to shoot good groups. It had a fast twist of 1 in 8. Barrel length may be one factor to your question.
     
  4. liltank

    liltank Well-Known Member

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    I have been shooting a .308 for 4yrs. It has been my conclusion that 1:12 is all a perspective user of the.308 needs. I initially had a 1:10 twist. This caused higher pressures in heavier bullet loads. I have found no evidence that a 1:12 twist barrel is any less accurate than a 1:10. For the weight bullets a .308 can fire efficiently, the 1:12 will handle anything you can put in it. I have had success with bullet weights up to 210gr. However, my current accuracy of .25 to .4 MOA is with 175 Nosler Custom Comp hand loads out to and beyond 810yds. I have also had success with Hornady 178's with .25 and .5 MOA groups. This is of course with an aftermarket barrel (1:12), but most factory barrels will do just as well with proper break in and ammo. The CZ is a very capable rifle. I have full confidence that it will fulfill all your needs. Just a little FYI, the 1:13 twist used by Palma shooters will stabilize up to a 180grn bullet. Have fun and hope you enjoy your new toy.

    Tank
     
  5. blipelt

    blipelt Well-Known Member

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    Tank have you ever tried to see if the faster 1:10 will stabilize a little better when the projectile goes subsonic? Get a little more distance out of her. Just something someone visited with me once.

    Brent
     
  6. WildRose

    WildRose Well-Known Member

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    This rifle is built specifically as a varminter, that's why it has the slower twist rate than a tactcal or "hunting model".

    Stick with the 150's or lighters bullets and it should work very well for you.
     
  7. Guy M

    Guy M Well-Known Member

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    The 1:12 twist normally handles up to 180, even 190 gr SMK's well. At least that's been the case in my rifle.

    I prefer to shoot the 155 - 175's from the .308 Win, but the rifle certainly handles the heavier bullets fine, even out at 600 yards.

    Regards, Guy
     
  8. Greyfox

    Greyfox Well-Known Member

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    I've had 308's with 1:10, mil-spec 1:11.25, and 1:12. Used them all with 168 and 175 SMK's. Haven't seen a difference in accuracy with these weights. I'm partial to the Mil-Specs with 168's. Seems to clean up faster, and I have shot as much as 200 rounds before cleaning and still hold zero, and accuracy , hot or cold. Accuracy good to about 2500 rounds. Would probably get more, but shoot hot frequently. Typical performance is between .25 and .5 MOA /5 shots.
     
  9. liltank

    liltank Well-Known Member

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    I've got to be honest I have not shot it far enough to give hard data. I have shot to almost 1100yds and impacts are consistent to that distance.

    Tank