Sierra manual says: IMR 4350- Min-57.8 grs, Max 67.0 grs ; H-1000- Min-68.5, Max-77.5 Doesnt have anything for the Retumbo.
My personal load that I use for the 200 SMKs is 64.5 grs of IMR 4350, CCI Mag primer, Win Cases, seated to a OAL of 3.530. And run about 2750fps out of my 26 barrel. Gets me about alittle less then an inch at 100 yards and do really well out past 300m.