but i don't understand when y'all say "black out"...
The 300 was designed to improve upon the imperfections of the 5.56 for short barrel subsonic guns. The 223 does not run very reliably in a short gas system and is hard as hell to suppress. The subsonic 223 is has terrible ballistics. The 5.56 also has less than effective ballistics past 500 meters.
The 300 fixes most of this. It has a very effective subsonic round inside 100 meters and suppression is very effective. It runs great in guns with gas systems shorter than 10 inches. It has similar ft lb knock down at 700 meters as the 5.56 has at 500.