Try some .430 300gr Hornady XTPs with the green MMP or Harvester sabots, they work well for me...
Where are you in NC??? I have a few that I picked up last year, I'll give you a dozen to try and see if they groiup in your rifle...
I'd also suggest going to loose powder so you can match the charge to the bullet...By going with 2 pellets, you are trying to find a bullet/sabot that shoots well...When you go to loose, you pick the bullet/sabot combo and then work with the powder to get a good group...