The problem with SMK95, which I believe is the best bullet offering from Sierra for Valkyrie, is that there is not many powders that are top tier..you can use for it, without sacrificing velocity hugely.
The main powders for this bullet are not temp stable. like RL17. Horrendous temperature instability. I should pick on that one, most in this narrow category have that issue. I was SO HOPEFUL StaBall 6.5 would be SO GOOD in Valkrie. ITS TOTALLY NOT! Not because its bad accuracy, its merely average. But because you just can't get enough in the case to get decent velocity. Its simply too slow burning to be considered "good" in Valkyrie I think. 28 grains in the case is all the way into the case neck, before you massively compress it to get the 90 grain in. To get the Velocity I want, I would have to put in probably 29 grains. No way that can work well, that is all the way to near top of case almost. I WISH StaBall was just a bit faster. A tad faster than H414/W760 would be IDEAL in temp stable ball powder for 5.56 and Valkyrie. But then again, thats why its called 6.5 and not 224! lol