Re: vertical stringing of shots?
Try shooting with a proper pedestal front rest and rear sand bags. If you are shooting off a solid bench (concrete), a bipod can bounce.
Voila, stringing. 100yds is too close for most tuning problems to show up. That is why I have always suggest shooting further while testing.
If using BH match ammo, I will give it the benefit that its well loaded and consistent. So look at the rifle as the main culprit.
Are you using the factory plastic stock? If so, you must bed it (you actually can with the right bedding compounds and prep) and free float that barrel. You will need a BIG gap.
With the better front rest and bedding, should solve your problem. Assumed that scope and mounts are ok. Check scope bases, they do loosen.