So, I had a load for my 75ELD that was a humdinger on my 18" plate at 1180 yards. RL15. Then I accidentally ruined my last 8# of it by mixing in some 2015. Devastating. Can't find RL15 anywhere. But my 25.5 grain load (Hornady brass) varied wildly with temperature, and had sh!t for SD - 25 fps SD was typical. So even though it was screaming at 3025 fps in summer (2950 in winter) and shot around 1/2 MOA, I asked some of you for suggestions above for a VARGET load.
My SD with varget 25.0/Hornady brass/205M were about 18, so first thing I did was prep some old Lapua brass (I used hornady for the extra 1.0 grains H20 capacity: 30.5 grains H20), and reduce the charge from 25 to 24 and 24.5 (cuz lapua lower capacity: 29.5 grains H20) and that latter load looks like where the money is for my SAC barrel (loading on a supertrickler, so all are +/- 0.02 grains). I'm losing about 60 fps compared to RL15 but gaining temp stability, more accuracy, and lower SD (which is probably the brass). Thanks for the guidance guys!
(And yes, I'm shooting 10 shot groups now after the Hornady #50 podcast. FOr 223 its not a problem and I have a mattress inflator that I use as a high CFM barrel cooler, so I just shoot a string and then blow it for 5 minutes and then repeat.)