Forget the "numbered" contours. Go to Lilja's site and Pac-Nor's site and see if your rifle is listed among the standard factory contours they replicate. It's a lot less hassle to work with a factory contour than some intermediate bastardized size.
Twist ... if you want to stick with 52s or lighter, no reason not to go with a 1-14" twist. If you want to run 55s, I'd go with a 1-12" twist. I've had some .22-250s with nominal 1-14" twists that would handle a 55 and some that wouldn't so ... take the fight out of it with a 1-12".
Tom
