Twist for 6.5 CM

[AK Hunter]

How much twist do I need to stabilize 147gr ELD round through a 6.5 CM?
The heaviest I have shot was 140gr & it shot good. I happen to find a box of 147s & wondered if I have enough twist to load some up for a try out, or if I just need to trade them off for something that will work in my gun.

 

[Jim Watson]

I found a thread that said an 8.5 twist was adequate, even printed on the box... in 2017, maybe they have quit offering suggestions.
https://www.65creedmoor.com/index.php?topic=7340.0

 

[AJC1]

Check out the Berger or applied ballistics stabilization calculators.

 

[jmr40]

I tried a box of Hornady factory 147's and they all shot fine in my 8 twist barrels. Looking at Bergers twist rate calculator their 144 gr bullet is rated as comfortably stable. Their 153.5 gr bullet is considered marginally stable. This is what they said about their 153.5 gr bullet in an 8 twist barrel.

Your bullet is MARGINALLY STABLE.
Your bullet stability is marginal. You may shoot good groups under these conditions, but the BC of the bullet will not be optimized.

Twist Rate Stability Calculator | Berger Bullets

Understand that these numbers are for BERGER bullets. Hornady bullets will be similar, but somewhat different. My guess is that the Hornady 147 gr bullets will be just fine in an 8 twist barrel. At worst the BC printed on the box may not be accurate which could mean lower performance than expected at long range.