Vertical stringing can be induced by the shooter, usually through cheek weld. It's effect is more prominent with lighter rifles It's not really a "weld". There's all kinds of ways to hold a rifle but give this a try before you spend money. Mind where your stock lays on the front bag. I don't stress to much about the front stud but I do slide the rifle fore and aft a couple times to see if it's sliding smoothly. If it's not sliding smoothly on the front bag or hanging up on the stud, do something so it isn't. The idea is to minimize shooter induced inconsistent stress while sending several consecutive shots downrange. Because I usually let my barrel cool several minutes between shots, I come off the rifle so getting back on the rifle should be similar from shot to shot. I mention it in steps but after a while, it will only seem like two steps because your doing everything else automatically like knowing the exact spot your car keys go into the ignition. Get into position behind the gun and adjust both your gun and your body so the when your relaxed, your crosshairs are pretty much right on target. Give a long blink. If you open your eyes and your crosshairs aren't where you want them, it's because your twisted up. That's cool because you caught it in time. Re-do your positioning so it's natural and get comfortable behind the gun.
1) hold pistol grip medium hard like your shaking hands with your thumb riding high over the tang. It's not a death grip. DO NOT pull the rifle into your shoulder. Just hold it. This is unnatural but important.
2) Instead of pulling the rifle to you, flex your pec muscle a little so the rifle butt sets against a firm consistent surface and push into the rifle with your pec muscle/shoulder but like I said, don't pull it into you. Your off hand can be used to make micro adjustments to the rear bag, or lay it without tension over the scope to mitigate jump or just hold the stock without inducing fore or aft tension. You'll need to experiment. I use my off hand to make micro adjustments to the rear bag.
Lay you cheek into the stock hard and then back off cheek tension so that, that part of your cheek that contacts the butt stock is just a reference point on the stock and not a tension inducing weld. I mention "lay it in hard" so you have a feel for how much you back off each time. No cheekbone, just flesh.
4) Center up the edge shadow in the scope.
5) Important: Control your breathing and squeeze the trigger deliberately to the center-line of the butt and watch your hit on the target regardless if the rifle jumps off target. If you can't see the hit, imagine the hit with your minds eye but in your mind, follow the bullet all the way out the back of the target. I try to hold the trigger to the rear until the target is hit but I don't know if that's right or not.
Because your not pulling the rifle in hard, it will recoil a bit more so I'd avoid creeping up into the scope to much till you've tried it out a little bit. The proof is on the target. If it helps, cool. If not, then do something different. Just for kicks, if you want to see vertical stringing, lay your cheek into the stock/weld inconsistently hard and pull the rifle into you with varying degrees of tension.
