Re: Extreme vertical spread at 100 yrds?
Use a supressor, don´t hold the pistolgrip too firmly, when squeezing, chrony your ammo and calculate POI@100yrds, std dev and the works. I have MOA accuracy with Eley Teenex selected batches. SAKO P72 biathlon version with a 1/2UNF threaded 40cm long bull barrel. I shoot with an oversized A-TEC modular silencer. Reduces recoil a lot.
I suggest you start out shooting prone with a single front rest (bipod!?!) and plenty magnification...
Learn to shoot between heartbeat by correct breathing and watching the reticule move vertically. Squeeze and follow through. One hole 25yards and excel from there.
Shoot a lot