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22 cal 80 gr Amax an 1-6 twist

5mmgunguy
Will a 1-6 twist stabilize the Hornady 80 gr a-max? There is a formula to calculate whether or not if the bullet will stabilize I just can't find it in any of my books...anyone help?
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5 comments

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  • Hawk Carse
    That is more than you need. I have a 6.5 that is plenty for 90 gr SMK and VLD. I THINK an 8 twist will stabilze an 80 grain, I am sure a 7 will.

    I would not bet the price of a barrel on the Greenhill Formula.
    I would apply one of the more complex stability formulas and then check THAT against what barrel makers, bullet makers, and actual shooters like nononsense say works in the field.
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  • dcs shooters
    It might. I'm shooting 69 and 77's from a 1/8 twist Douglas 223, and getting 1/4in groups at 100yds.
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  • rufe-snow
    quote:Originally posted by 5mmgunguy
    Will a 1-6 twist stabilize the Hornady 80 gr a-max? There is a formula to calculate whether or not if the bullet will stabilize I just can't find it in any of my books...anyone help?



    GOOGLE is your friend, it's the Greenhill Formula
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  • nononsense
    5mmgunguy,

    In answer to your question, no you do NOT need a 1:6" twist to keep this bullet stable. In my .223 Match rifle, I use a 1:8" twist for this bullet and the 80 gr. Berger VLDs, both perform just fine.

    I use the 1:7" twist barrels for the 90 gr. JLK VLD bullets.

    Here is a link to a twist rate calculator which also has an explanation of the Greenhill formula:

    http://kwk.us/twist.html

    Here is a set of ballistic links from our friends up in the cold and frozen north:

    http://accurateshooter.wordpress.com/2009/04/25/free-ballistics-calculators-and-data-charts-from-canadas-nfa/

    And another that will work with alternate variables:

    http://www.uslink.net/~tom1/twistrate.htm

    Best.
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  • 5mmgunguy
    Thanks!
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