As well as in shorter barrel lengths (~eight″) the 300BLK is much exceptional for supersonics, at the very least. Prolonged barrel 300BLK is near pointless IMO, you'll find other rounds that outperform it handily in the exact same System, with very same length barrels. You'll need to tweak subsonic handloads https://ruhollahb947dnx3.wikiadvocate.com/user