I have 2 6.5 Creedmoors, a Bergara B14 Wilderness Ridge and a Ruger American Predator Go Wild. With the Bergara I like the Sierra 123 grain Matchking at 600 yards. It’s very accurate, well under half an inch at 100 yards. I haven’t worked much with the heavier bullets. Was going to earlier this year but the weather wasn’t cooperating for accurate rifle shooting. I’ve been shooting handguns.
For powder, so far, I prefer IMR 4451 over H4350 in my rifles. Seems most people prefer the H4350 or one of the Reloader series of powder. For primers, CCI large rifle seems to be the best for me. But Remington 7 1/2 works good for me, also.
As I said, 600 yard accuracy is fantastic with the Bergara using the 123 Matchkings and IMR 4451.
Just a slde note, each of my rifles are more accurate and consistent with the muzzle break off.