You can get both subsonic and supersonic rounds. Typically anything under about 160gr (projectile weight) is going to be supersonic. Subsonic's go up to about 220gr or 240gr (easy to locate 220gr). Uses the same projectiles that you would load into something like .308 Winchester...
Both subs and supersonic depending on what you want to do. These are 220 subs they run great in a semi ( or full auto ) you can get them with a little less powder for bolt guns but truth be told these are mouse fart quiet out my Remingtom 700 300aac with a can.