Re: Rate of Twist?
Velocity is the other factor in what twist rate you need. The .22-250 pushes a given bullet faster than a lessor cartridge like the .223. ...so, with the same projectile - the .22-250 will need less twist to stabilize the bullet.
1:12" is generally plenty with your average bullet selection with the .22-250. Should you go with a really long bullet, then you might consider a faster twist.
If you have to track your game, then you aren't using a big enuff gun.