Not in a 300 win mag, but in a 7mm mag with 180 Bergers I have. The H-1000 and RL-26 were very similar in accuracy at 100 yards, from .3 MOA to .6 MOA in a factory Remington, but with the RL-26 I reached 3023 fps and still wasn't getting over pressure signs, with the H-1000 I was seeing over pressure signs at 2980 fps, and also H-1000 had terrible E.S. numbers, 30 fps on the low end, and 50 fps on the high end, with only 3 rounds...but the RL-26 had a low E.S. of 7 fps and a high of 13 fps. That is just my experience in one rifle with one bullet type in a 7mm mag.
Mirrors my experiences exactly, except I'm running RL26 and H1000 in a 300 win mag pushing the new Hornaday 225s.
Still working up to pressure, started way low, but RL26 was consistently better than H1000 in my rifle. Sds are in the single digits with es running low double digits to high single digits. H1000 was Sds of 30ish and es of 60-70 in most of the loads. Not sure if that will settle down once I get into a better node but so far it's not looking great for H1000..
Best groupings with each powder were around a third of an inch at one hundred.
Specs:
Factory remington 700 long range in an XLR Carbon
Virgin nosler brass, no prep
CCI 250s