I am doing something similar, the 143 eld x, stevens action, er shaw sporter barrel in 260 the best that I can measure mine is 2.900 to lands with the eld x, I tried approx .005 jump @ 2.885 / approx.048 off @2.852 / and approx 60 off @ 2.829 with a start load of h4831 at 100 yards they all shot around .700 in groups all having two touching and one flyer opening them to about .686 the only thing that really stood out was the .048 off group was flat with no vertical, I may retry again at 200 yards because of the flyers and I am not a 100 % sure what group was the best