stage of Service Rifle all the time, they do, and HAVE done so, for about 10 years now. The Advanced Marskmanship Unit abandoned the M14 and 308 in favor of the M16 and 223, for match shooting, when a WOMAN Marine kicked everyone's ass at the Nationals, using an M16, back in 98, I think it was. The better 80 gr vld loads, with 24" barrels, still have 500+ ft lbs left at 600 yds. In other words, a 223 user, if he knows what's up, CAN hit harder at 700 yds than a .45 ball rd hits at 7 ft(ie, 400 ft lbs).
Just because you are stupid, and only know about 55 gr, plain based softpoints, in 20" barrels, doesn't mean that better performance cant be had. It just means that you are ignorant, that's all.