I just got my gun back from Remington (read, NEF, then Marlin, then Remington)
My Ultra Varmint Fluted .204 barrel was BAD. Oversize, no accuracy, etc. Remington confirmed this, replaced the .204 (with a NON Fluted barrel) and I paid for a .223 barrel to be fitted.
I can now shoot MOA with both barrels. Mike Scherz (developer of the 550 Magnum) inspected the barrel and showed me how bad it was...
Problem: No fluted barrel, and it took them 3 months.....good luck