I may have handicapped myself with a 1:8, 22" 1.5 contour Shaw barrel. On a standard length Mauser I get the full 3" and then some to play with. Current load is Sierra 100 gr GK atop 43 gr of IMR 7383 (Surplus powder) for 3000+ fps, for a lope hunt coming up here in a couple weeks, accuracy is right around 3/4" at 100 yds. So for me it was standard length action with a shorter barrel. As far as twist, that all depends on your purpose for the rifle.
