1:8" Twist is good for any weight and length, the Nosler 125 grain Partition bullet at 2,800 fps and above has a Stability Factor of 2.367 in the 1:8" twist, where anything over 1.5 is stable (Miller Formula).
I barrel all my long action magnum capacity rifles with 26" barrels.
Remember that Winchester loaded the original .264 Winchester magnum with a dual diameter bullet that was bore diameter just ahead of the canelure, so it could be seated out and still work in the magazine and standard throat. Select the bullet you wish to use, then make up a couple of dummy cartridges that place the bullet out where they will work through the magazine, but stay out of the powder space as much as possible. Then have the chamber throated by your gunsmith to fit that OAL. A slightly longer throat is better than one too short. Same if you plan to use factory ammo, select the heaviest weight bullet and have the chamber verified for that combination.
Last edited by WranglerJohn; 02/25/11.
