Re: Twist rate on .308 for medium range
The 12 twist will work just fine for the 168 and 175 SMK. The 175 will remain stable out to 1k with the 12x provided you launch them with at least 2400 FPS. No need to over spin your bullets.
I you need to shoot a bullet much bigger than the 175, then think about a 11 or 10x
Or hey if a 10x gives you the confidence you need, by all meens use a 10.
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.