Replacing barrel. What twist should I use ?

[LouisianaHunter]

I'm planning to rebarrel a Sako AIII . Going 7mm Rem Mag. Probably 24" . I probably will be shooting bullets in the 140-160 range , but would like a twist that would handle up to something in the 175 range . Is there a chart you go by or just experience ? Thanks

 

[MagnumManiac]

Standard 7mm twist is 9.5", but 9", 9.25" have been used by the factories and all 3 will stabilise bullets up to and including 180g. My STW is a factory 9.25" twist barrel and will handle 180g Berger bullets, however, it won't stabilise 195's.
If you want real heavy bullets, a 1:8" twist is recommended.
If you want to shoot 175's as max, then go with a 9" twist.

Cheers.

 

[LouisianaHunter]

Thanks, any advantage to 1:9 over1:8 ?

 

[MagnumManiac]

Well, the ONLY advantage going to a 8" twist is to run heavy for calibre bullets.
It makes zero difference to everything else, even a 120g will still work in a 8" twist.
People believe you can over-stabilise a bullet, not true, you can spin a bullet so fast that it is pulled apart by centrifugal forces, but it's still stable up to that point. There is only stable or unstable with bullets.

Cheers.

 

[L.Sherm]

There is such a thing as spinning a bullet that hurts jacket integrity which equates to poor accuracy.

 

[MW204]

Here's the chart from Shilen rifle barrels.