H1000... still waiting on my 300 PRC to show up though.
Ladder test through Unknown Munitions was an amazing starting point with my 300 Win Mag, found the node +-.2grains where I could load myself as I don't have a FX120i
I was off to the races there with my 215 Berger Hybrids on seating depths.
Call up Steve at Hammer Bullets and ask him what he recommends. There are many good choices out there, hodgenreloading has their loads for a 200 gr bullet plus RL23 / RL26 and N570 should work very well.
My guess Steve will recommend RL26 to start because the hammers are all about getting speed.
If any of you folks are in MN and want some of the magic high velocity fairy dust (RL26) I've got an unopened 8 lber I'd happily exchange for the same in H1000.