Determine AR twist?

[waynewal]

How do you determine a bbl twist?

Have a no name upper from many years ago. Used a 25 power scope at 100 yds on the AR15 Hvy BBL upper for group testing.

There is no marking for a twist, no number I can see after field stripping.

5 rds WW 55gr ball, handheld resting on bench shows about sub 3/4" group.

5 rds. Black Hills 68gr HPBT Match sub 1/2".

Rds are imapacting about same place, with the 68gr about 1/2" lower than the 55 gr.

Doesn't seem to be 1/7 as my Military exp. shows the 55gr are terribly skewed. Possibly 1/9 twist since 222 yrs ago that was a good average for those who used both bullet weights.

thanks!

Wayne

[outerlimits]

easy-put your cleaning rod thru the barrel then add a patch to a loop. get some tape and wrap it around the cleaning rod on the other end pointing up at 12 o'clock. pull the patch thru and watch the rotation of the tape till it gets to 12 o'clock again and measure. hard to describe but it works.

[waynewal]

easy-put your cleaning rod thru the barrel then add a patch to a loop. get some tape and wrap it around the cleaning rod on the other end pointing up at 12 o'clock. pull the patch thru and watch the rotation of the tape till it gets to 12 o'clock again and measure. hard to describe but it works.

Thanks! will give that a try!

Wayne

[waynewal]

easy-put your cleaning rod thru the barrel then add a patch to a loop. get some tape and wrap it around the cleaning rod on the other end pointing up at 12 o'clock. pull the patch thru and watch the rotation of the tape till it gets to 12 o'clock again and measure. hard to describe but it works.

Thanks! Worked great! It is a 1/9 twist! Works great with my 55gr and the 68 grain <=100yds. Will try longer and see if it is stable.

Thank you,

Wayne