Very interesting feedback.
Congrats on your success. I am really surprised getting that kind of grouping out at 50 with that light of boolit and light loading.
What brand of boolit and where did you get them? Not aware of any swaged 100 grainers in states.
This being a semi wadcutter, I assume you mean shoulder of boolit 1/8" below case mouth?
What is your make of PPC gun? What twist in bbl? Bore diameter? Why is it only Winchester brass will work in it???
You are correct in concentrating on windage dispersion as opposed to elevation for grouping.
You pic showed up and that is impressive grouping. Is this consistant? Have you tried 24 rounds for a group considering this is what you will shoot from 50 yards? Considering factory advertised velocity for 149 grain full wadcutters is 702-720 this is surprising to me.
I could never get a taper crimp to give me same accuracy of a light roll crimp. What brand die are you using? What is the diameter of these bullits?