Its more consistant from lot to lot right now and from what I see and from my customer reports, US869 can be as quick burning as Retumbo and a slow as AA8700. Pretty wide range.
This is not uncommon with a new powder, Retumbo was the same way for the first several lots and then seemed to even out.
I order all my WC872 from Jeff Bartlett at www.gibrass.com
Its fresh powder, never loaded or pulled and you just know what your getting with Jeff. $40 per 8 lb keg is pretty cheap.
Yes it burns a bit dirty but if you run up to upper pressures its no worse then any other ball powder. It is also a bit more sensitive to temp changes but for big game hunting this is really not a huge issue unless you load to red line pressures which I do not like anyway.