Managed to find a load under 250gr bullets that works well. 59.5gr RL 15.5 in once fired Nosler brass, CCI 250 mag primer, 3.34 COAL (3.33 also worked but crunched powder), 250gr partitions.
2500 fps in a 20" barrel (shorter than SAAMI throat) ES of 18. I could not get any better than 3/4 MOA but it always gave nice round groups. I tried swapping in CCI std primers, no change in either velocity or ES or group size. Tried WLRs and the groups got slightly bigger, velocity was basically unchanged.
Worth noting that 59.5grains won't fit in unfired nosler/norma brass: it comes almost to the top of the case. But it will fit in once-fired Nosler/Norma and once you settle it (electric toothbrush) a 250 partition (or Speer) will seat at 3.34-3.335 COAL with no powder crunching (or minimal).
3/4 moa is plenty accurate for what I plan to shoot with a 250gr partition, but it's not a particularly accurate load for this rifle. With either 250 speers or 250 partitions, RL-15 gets 1/4-1/3 moa, so does IMR-4895, and so does PP 2000-MR. The RL-15 and PP 2000-MR groups are also going about 50 fps faster so it's possible there is just a higher accuracy node for this rifle that I can't hit with this powder.
But for the (still unproven) temperature stability, I'll take it.
Is this better than Varget? Probably not, but I've been stingy with my Varget supply as I've got other things I need it for. In some very quick and dirty testing, 57 grains of Varget in this rifle did more or less the same thing.
