I have a 6.8 SPC upper that I built, and I recently purchased another 6.8 upper (I wanted a piston upper), so I will likely be converting the one I've built into a long-ish range (300-600) gun. I will need to sell my Wilson Combat barrel either way, but with .224 Valkyrie, I can reuse the BCG and mags. However, the round has not proved itself yet. I don't have much experience with Grendel, so I don't know much about it. Have the issues with bolts been fixed? Are magazines available? How affordable is decent ammo? I'm still doing my homework. I could also go with .223 Wylde and 18" barrel for an SPR-esque build (ammo/mag availability). Do Valkyrie and Grendel offer much advantage to a long-range noob? I am still digging around them internets for data, but I was wondering what experiences fellow forumites might share.