I use H-1000 in my F-Class .300 win mag AND my winchester model 70 super grade hunting .300 win mag.
It is THE ideal powder for the .300 win mag for bullets ranging from 180-225 grains. It has the lowest extreme spreads, it is extremely temp stable and it fills the case well.
One thing about it though, It seems like H-1000 likes to have bullets seated long? I have no idea why this seems to be the case. Coincidence?..probably. But every time I have done a load workup with H1000, I didn't get down below MOA until I pushed the bullets closer to the lands.
I know that powder probably shouldn't affect seating depth the way that a bullet likes a certain jump. It is true that seating depth changes pressure for a given charge, but I have always thought that the only thing seating depth changed was how much powder you could fit into the case, and you adjusted the charge....well, with H-1000 it seems to perform better with bullets seated out beyond SAAMI spec.
The other thing with H-1000 is that it performs best with a compressed load, which means using longer heavy bullets. AND a Magnum primer. either Federal 215 or CCI -250. I don't care if it is a .270, use a magnum primer. I use H-1000 in .270 seated long and a compressed load and shoot bugholes with a 130 gr accubond.
But if there is 1 cartridge that H-1000 seems to have been meant for, it is the .300WM.
I have lots of info on this powder, just ask via PM if you want to know more.