I have a 6.5*47.
Current barrel on it is a Bartlein 1:8.5. the previous barrel was a Shillen 1:8 which didn't shoot as well. Unlikely the difference is related to twist... Different barrel manufacturers, different gunsmiths.
The 8.5 shoots the 130 Berger AR Hybrid well, but not the Nosler 140 CC. The 1:8 twist barrel didn't shoot the 140's very well either. Too many variables to say with any confidence this is related to twist.
Berger has a twist rate calculator on their website where you can input your own data or use their bullets. I am not necessarily recommending their bullets but it's a handy stability calculator for what you are trying to do;
http://www.bergerbullets.com/twist-rate-calculator/
As we know stability degrades with velocity so you can input expected velocities at hypothetical distances to see whether your intended bullet is still comfortably stable. Also not a simple as choosing the most stable bullet at distance because after apogee (roughly 2/3 downrange) you don't want it so stable that it will resist pointing to the target on the last 1/3.
You're pretty safe with 1:8 and certainly no slower than 8.5.
Current barrel on it is a Bartlein 1:8.5. the previous barrel was a Shillen 1:8 which didn't shoot as well. Unlikely the difference is related to twist... Different barrel manufacturers, different gunsmiths.
The 8.5 shoots the 130 Berger AR Hybrid well, but not the Nosler 140 CC. The 1:8 twist barrel didn't shoot the 140's very well either. Too many variables to say with any confidence this is related to twist.
Berger has a twist rate calculator on their website where you can input your own data or use their bullets. I am not necessarily recommending their bullets but it's a handy stability calculator for what you are trying to do;
http://www.bergerbullets.com/twist-rate-calculator/
As we know stability degrades with velocity so you can input expected velocities at hypothetical distances to see whether your intended bullet is still comfortably stable. Also not a simple as choosing the most stable bullet at distance because after apogee (roughly 2/3 downrange) you don't want it so stable that it will resist pointing to the target on the last 1/3.
You're pretty safe with 1:8 and certainly no slower than 8.5.