Have been cyber stalking this thread since the news broke on the 224 Valkyrie. Color me very interested especially the SURG 11.5" uppers shown with the pinned muzzle attachment. Could really see the 11.5" and 22" making a great pair for 224, Fusion 100gr for the 11.5" and 90 gr for the 22". Especially if the outside tube of the suppressor is the serialized part and could be shared between uppers.
Another bit of news I saw this week has me even reconsidering a 300 BO option. Hornady apparently has developed a 190 bullet for subsonic use in 300 BO that meets FBI penetration criteria (at least out of a 16" barrel, but I don't believe 300 BO loses FPS as fast as 556 so your 12" should be fine). To the best of my knowledge this is the first subsonic 300 BO round with real penetration and expansion data form a major ammo manufacturer. I played with a 9" factory AAC upper before and could never get reliable function switching between Barnes 110 gr black tip supers and even the Remington range ammo, much less sub sonic loads. And that wasn't even factoring in a suppressor.
I suspect with your low blow back pressures being seen in the Tranquilo and likely carrying over into the SURG that switching between the Barnes super load and a quality sub load like the Hornady will be uneventful.
Two thoughts about the 11.5 SURG uppers with the pinned brake:
1) Love the fact that they are not Key mod and standard threaded 3, 6, and 9 for the polymer grips. That has always seemed to work well on my 12" OBR and 14.5 tOBR 762, keeps the heat down, good grip, and light weight. However, I would love to see the hexagon cutouts at 1:30 and 10:30 replaced with Mlok slots. For those of us that don't need the QD function for WML there are some really slick, low profile, light weight mounting options that really shine at those positions on the handguard.
2) I know FDE is the new "Tacticool" color, but please consider the option of good old fashioned black. Black was the original "Tacticool" before anybody knew what "Tacticool" was.
And with that, I will patiently wait the next 2 weeks till I can place my orders.