I've only had one 18" 6.5 Creedmoor barrel, but I've had pretty good luck so far with N150 and 123 Scenars.
Approx. ~2850 fps with 40.0 grains N150 and Norma/RUAG brass. No noticable pressure signs. ~3/4 MOA accuracy.
Would have to look at my reloading book for SD's, but it was probably...