Looking to pick up a 6.5CM and pull the barrel and throw on a 308, mainly running 150sst and 169smk.
Would a 9 twist be better with a 18” barrel for velocity or a 10 twist?
Would a 9 twist be better with a 18” barrel for velocity or a 10 twist?
- Thread starter Jmccracken1214
- Start date
Put everything you know in to this calculator and see what you need…seems for those bullets you could probably go for a slower twist….at least 10 maybe as much as even 12. Maybe try a gain twist if you want to get fancy.
bergerbullets.com
Twist Rate Stability Calculator
Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.
bergerbullets.com 10 is most versatile, but 11 or 12 would be fine for those projectiles. I shoot 208 eld-m's out of my 11.25 twist.
i just ordered a 1-10 for 308
Why not just buy a .308?
longer (read: heavier) bullets need faster twists to stabilize. What you mention is bread and butter 308 rounds. 1:10 is a fast twist for 308.
1:11 and 1:12 would be fine for those bullets.
a 1:10 would be fine for the "lighter/faster bullet, more twist" concept that sensei lowlight often talks about.
1:11 and 1:12 would be fine for those bullets.
a 1:10 would be fine for the "lighter/faster bullet, more twist" concept that sensei lowlight often talks about.
When the time comes, my TRG will get a new 1:10 twist barrel from either Bartlein or Kreiger when the factory tube is toast. But with about 2500-3000 rounds down the tube so far, it will take some time.
Twist for the most part does not effect velocity. This has been proven over and over again. I even have pressure and velocity data from ammunition pressure test barrels. No difference if your running a 8 twist or a 12 twist etc...
For the bullets you are using.....no need for anything faster than a 10 twist. Even a 12 twist will handle up to conventional jacketed bullets up to 190gr. A faster twist with crappy bullets/ammo will amplify any issues the ammo has and can have a negative impact on accuracy would be my main concern.
Earlier this year....I finally got a second barrel made for my AIAT. One barrel is in 6.5CM and the other one is in 308w. The 308 barrel is a 10 twist and finished at 20". Might cut it down to 18" as I pulled it off so I can thread it for my suppressor attachment which finally came 2 weeks ago. It's been a laser beam with the 10 twist. I'm not shooting anything heavier than a 175gr bullet.
Later, Frank
Bartlein Barrels
That's what I am doing, why barrel swap.
