Advice Please. Rate of twist??

[Billy52]

I am getting a rifle re barreled in 257 Roberts.....I was wondering what rate of twist is required to stabilize a 115-120 grain bulletin this caliber?? Any input would be greatly appreciated. I've googled it and tried to do some research...but have not decided yet.
Thanks.

 

[guntech]

Did you look at Shilen's website?

http://www.shilen.com/calibersAndTwists.html

.257
- 9" for bullets heavier than 100 gr.
- 10" for bullets up to 100 gr.
- 12" for bullets up to 90 gr.
- 13" * for bullets up to 80 gr.

 

[Billy52]

Thanks. Looks like 1 in 9...cheers.

 

[mooncoon]

there is also the Greenhill formula which is T = 150 D squared over L and note that the formula also goes the other way; L + 150 D squared over T. The formula is the bare minimum to stabilize a bullet of a given length and most people make the twist rate 1" faster than the formula. There are constants (mulitpliers) to correct for peculiar bullets (say aluminum or depleated uranium) but the formula seems to work well for convential bullets. The formula was developed in the 1870s by a US artillery officers for artillery projectiles (unless I am mistaken)

cheers mooncoon