Those are some pretty impressive results, especially with factory ammunition. Federal GMM has an excellent reputation.
You are honestly the first person I've come across who has had such success with the Valkyrie; accuracy in mass-market Valkyrie rifles has reportedly been mediocre. Which company manufactured your rifle's barrel?
I too have had excellent results with Valkyrie in 24" HB side charger upper. Run about 300 through it in slow fire. Now I culling the gunsafe as I cannot close the door. It and the Grendel are going as I'm into subsonic suppressed now.