I know the rifle is new, but I'm just wondering if you could use .020 patches?
Another thought: Punch up the charge to 90 grains of 2F, and use a pre-lubed .54 cal wonder-wad underneath the PRB combo that you're using now. The extra 10 grains will get the ball out to the 100 yard target just a little quicker so wind will have less time to affect the ball. The wonder-wad will give you a little more lube to soften the fouling even more, as well as lower the SDV, thereby tightening the groups. And the wad will also help protect the .018 patches while you're still breaking-in the rifle :wink:
On any given day, heat, cold, humidity, wind, caffeine, changing sunlight on your sights all work to open-up your groups. Take notes as to the behavior of your rifle under different circumstances, and learn to make adjustments with good ol' Kentucky Windage & Elevation.
Most rifles can shoot better than their owners! I know mine do! How else could I cut playing cards in half!
Good luck with yours :thumbsup: .
Dave