What is the most twist rate for the 40gr projectiles?
This new cartridge seems to have excellent accuracy from early reports?
APB

APB-- The factory .204 Ruger rifles have a 1 in 12" twist. Some rifles seem to thrive on the 40 gr. bullets and other don't seem to shoot them worth 2¢. My personal opinion is that the 1 in 12" twist might be getting close to a wee bit too slow for the 40 gr. projectile. When I rebarrel my Savage 12VLP it will get a barrel with a 1 in 11" twist to enable me to stabilize those 40 gr. bullets a little bit better.

A 40.0gr Hornaddy bullet 0.749 long will be stabilised with a factor 0f 104% in a 1-12 twist with a veloccity of 3850 ft/sec MV. The recommended stabilizing factor is 125-130%.

A 1-11" twist will stabilize the bullet at the above numbers at 125%, and a 1-10.8" twist will stabilize the the bullet at 130%.

So a 1-12" twist will just marginally stabilize a 0.204 40gr Hornady V-max. A certain Mr A.R Sole will call the above arm chair mathematics and judge them totaly meaningless. Try them in your rifle it might like green eggs and ham Sam I am.

The Berger Bullets Online Catalog has twist rate recomendations for various bullets. Interesting reading.