13" twist would be nice for the Berger target bullets,... BR column, 65 BT target and the 68 FB target.
Problem is the #4 lilja contour is a skinny barrel, thus only good for things like coyotes with a 13" twist.
But the Berger 68gr FB target bullet in the 6mmRem out a 27" bbl should have no problems surpassing 3,900 fps with RL-17