H1000 won't get you great results. You won't be able to get enough in the case for maximum performance.
IMR 7828ssc is my new favorite powder in the 300 WSM. It is about as good as I have found for the slow burners and the ES in my loads have been fantastic. I worked up a 210 Berger load with 7828ssc last week and I had six straight duplicating velocities with one particular powder charge. I thought maybe the chrono was spewing some foolishness until I went to the next powder charge and started getting very close but different velocity readings for each shot again. I have found 7828 to be insensitive to temps ranging from 25* to 80* in loads using the 210 VLD and the 230 Tactical.
I like 4831sc for the 200+ bullets too, but the speeds on 7828ssc have been a bit better. I use a standard CCI 200 in Norma brass for all my 300 WSM loads now.
I have worked up some good loads with RL17 and the 200 Accubond as well, but they got a bit squirrely in hot temps. Great hunting round though.
Great choice on going with the heavies in the 300 WSM, they really sing with the high BC bullets.