Sorry for hijacking this one fellas…
Encore, what was the end result with your testing? I ask because I think I ran into this myself on my cva accura PR using BH209. I was getting vertical stringing and I was baffled because all of my loads were measured by weight, same bullet, primer, etc. what I did notice, is that the harder a seated the bullet (more pressure I applied) I lower it shot, which still doesn’t make a lot of sense to me. In addition, I feel like pressure I apply in the barrel as I am loading is extremely consistent right up until the bullet gets seated, when get an inch or two before I bottom out to the powder, it seems to get easier.
So besides all of that going on, my gun increased its drop at 200 yards by 4 inches consistently using the same loads, bullets, primers. I initially thought my sabot wasn’t fitting tight enough so I sized up- same result. I did get one size tighter to experiment with. I finally did find some more bh 209. This issue is eating at me.
290 grain t-ez
80 bh 209 by weight
Cci 209 m. Primers.