6.5 Creedmoor

[65Whelen]

I apologize in advance for a non Grendel question, but I trust this Forum when come to anything 6.5. I have a Savage 12 LPV 22-250, for a winter project I want to swap barrels to a 6.5 Creedmoor. My question, 8 or 9 twist. Primary intended purpose, target/bench and hopefully some long range deer hunting.

[Hank Rearden]

The two 6.5 Creedmoor rifles I've owned have both come from the factory with a 1-8 twist.
Savage 12lrp and Tikka Ctr.
Both shoot 1/2Moa with factory Hornady 140 AMax.

[Kilco]

Absolutly 100% 1:8. You will want to shoot 140's and up for target, and even hunting. 1:9 will limit you to 130gr.

[Klem]

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.

[Texas]

+1 on 1:8

[BluntForceTrauma]

I was reading on the 6.5 SAUM Facebook page the other day and George Gardner says they are moving from 1:8.7 to 1:8. Just one data point. Seems to be the trend, lately.

Bill Alexander always pointed out that the slower the velocity and the longer the bullet, the tighter twist needed. Thus, his 16" tubes are 1:7.5. His 24" were actually 1:9. And, as mentioned, if one plays with Berger's Twist Rate Calculator, one can get good data for any given bullet and velocity and environmental conditions.

Another thing to remember is that Bryan Litz testing showed that each inch difference in twist rate accounts for ONLY 1.33 fps average difference in velocity. So, if your 1:9 twist gives you 2851.33 fps, then your 1:8 will "only" give you 2850 fps. I see no real downside, only pluses, to the tighter twist.

[acourvil]

I was reading on the 6.5 SAUM Facebook page the other day and George Gardner says they are moving from 1:8.7 to 1:8. Just one data point.

I think for the Rem 260s and 6.5 Creedmoor they have been using mostly 1:8.2

[65Whelen]

Thank you gentlemen, confirms my thinking.