Moreover you must use a company Crimp after seating on subsonic hundreds. I like Lee collet crimp . Crimp will considerably Increase the consistency and minimize group dimension . You'll have to tweak subsonic handloads based on your rifle and the ambient problems so as to get consistent subsonic performance. https://reloading300blackoutaac16924.blogdiloz.com/37633282/5-easy-facts-about-brass-300-blackout-described