I am a big fan of 300BLK, own a company that converts brass, shot something north of 15k rounds, etc...
I have a bolt 300BLK
I have a bolt .308
Subs in either are just about equal sound wise IMO. Maybe on a meter you could tell the difference.
300BLK shines in the AR platform. In a bolt, meh, I dont know. I have it as a demo, I dont shoot it nearly as often as I have my .308 out. I also have a TC 300BLK that I am building up right now.
NOW, in states where you cant hunt with a semi auto, 300BLK in a bolt starts to make sense. I forget which states, but some states its illegal to hunt with a semi auto, but silencers are legal. DUR....
Delta4-3: I have never had an issue with subs in a .308. Probably loaded 3k with trailboss and a variety of bullets. I dont do any special brass prep although I tend to use worn out .308 cases with loose primer pockets and what not.