Twist rate depends on your choice of bullets up to 107s use 1 in 8 the 115 require 1 in 7.5. Now just to muddy the waters a bit the choice of calibers 6x47L, 6XC, 243Win or 243 Win ACKLEY. I'm a fan of the 243Ack, but any of them will work, some are simply more of a pain in the rear than others.
Enjoy. Bill