I think most factory 270's have a 1-10 twist. Would there be any advantage or disadvantage to having a 1-12?
I'm going to have an old Model 70 rebarreled, and here in my part of California, we have to shoot copper. I'm looking at the Barnes 110 gr. TTSX........just wondering about the twist for something lighter than the standard 130 gr.

Why?

Just added a couple sentences to my original question.....

copper bullets are longer for weight, which require faster twist -- would be a shame to build a rifle that wouldn't stabilize the target bullet

Like Jeff said. Bullet length not weight is the issue

That's makes sense.......The Barnes is quite a bit longer than the competitors lead cores in the same weights.
I better stick with a 1-10.

Thanks,

Ed

Obviously, SSG, you don't come from Remington. For some reason it didn't occur to them to ask the same sort of question before producing their 244 Rem and 35 Whelen rifles

I have a 250 Savage and 257 Roberts, both with a 1-10 twist. With Barnes 115 TSX, groups run 12-14 inches.

quote:

before producing their 244 Rem and 35 Whelen rifles

They just wanted to wait and bring out a 6mm with the right twist

Do a google search on the "Greenhill formula"... it's not perfect, but will give you the info you need to get you started..

Google JBM Ballistics. The site has several calculators, including Stability. You will need the bullet length, which is available on most bullet makers' web sites, including Barnes. You will find that you definitely do not want a 12 twist .277. The 10 twist is appropriate. You will get a stability factor from the calculator of something around 1.200 to 1.600. The US military specifies a minimum of 1.500. The calculator uses standard temp and pressure. If you hunt in cold environments, plug in a temp lower than 58F. Cold air is denser and results in more drag. It can make a significant difference. JBM uses the Don Miller formula which is more accurate than the old Greenhill's.

If you have a problem, PM me and I will be happy to help.
Brice

Pa.Frank and Brice........I looked at both of those sites, very interesting....Thank you!