I'm considering investing in a large amount of ammo. My gun is an M+P Ar15(m4) 16" with a 1/9 twist (common I know). I have a lot of experience with all types of targeting, mainly just with .223. the 16 inch barrel has suprised me with long-distance sharpshooting, i.e. 3 or 4 hundred yards giving a tight group of around "12 at that distance. (With .223.) I like that the NATO rounds pack more punch, but do we sacrifice accuracy with them as opposed to .223? Should I get some of both when I order, and if so should I 50/50? Assuming both have their pros and cons, I will buy some of each, but which one, if either, is more practical and how. And am I wrong about 556 being less accurate than 223 at long distances?