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?

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.

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.

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

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.

5mmgunguy

Thanks!