With 105g berger molly vlds and vit n560 av velocity of 3150 with my 243 1 in 8 twist barrel i noticed a lot of vertical stringing of groups at 100y 1 inch string bullet holes on target touching and climbing, with same components running at 3450fps group size was far tighter but doint think barrel will hold out to long running at that vl, question would changing to a tighter neck size bushing with my redding comp dies help tighten up vertical or could someone shed info with main causes of vert stringing thanks paul.