I went to 6.5 Grendel to dabble in longer range AR shooting. I've shot my 223 wyldd 16" out to 500 easy enough but I wanted something that would actually be useful at that range. I put together an upper with a 22" Satern barrel. It will shoot .3ish moa if I do my part with factory Hornady. I'm going to try and stretch it out to 800 or so when I can find someplace to do so.