... it seems that N570 excels with heavier projectiles and slightly longer barrels.
That would be logical. It's slower than H1000 by a few clicks. A few years back, people here reported mediocre performance for H1000 compared to others like RL26 or N565, so even though I've got plenty of H1000, I never gave it a try. I have piddled a fair bit with RL26, N565 and N568 and made one test with N570 and was not impressed. Note my barrel is 30" and I was shooting 230 gr bullets, so the heavier/longer would seem to apply but what I was seeing was higher MV SDs and just OK on-target performance with N570. I've shot the 300 PRC very little at short range, though and have spent most of the time with it at a mile or beyond, and shot the OCWs at 300 yards, so it's apples and oranges compared to showing tight groups at 100. My rifle is an AX-MC and it appears to be limited to ~0.5 MOA form the little bit of shooting I have done at 100. RL26 seems to be a unicorn lately but I am seeing N565 and N568 come available a few times a year. Fortunately, I have a solid supply of RL26, VV powders and 230's. Still not tempted to give H1000 or Retumbo a go. My current load is better than I am as a shooter.