we had the up close " house to house er mud hut to mud hut--" too.
308 could do it all but it is soo heavy -- try lugging 500 rounds of 7.62x51 up some mountain in afgainstan along with all your other gear.
5.56 is a might small , 7.62x39 is a bit "slow" and 7.62x51 is a bit "big" to carry around in bulk.
i think that is what the word "assault rifle" has come to mean - some kind of compromise.
the DOD ain't much interested in a new round. it thinks the 5.56 is cheap and thats what were going to run. end of story.
the m16a2s with the knight kit on them and a ACOG can hit way out there and the same goes for SAW type machine guns.
5.56 hitting things like bomb laden trucks can have problems getting through the sheet metal of a hard old truck at range.
you don't want to be close at all to one of these. we stuck m240s out there whenever we had um--the bad news is there are never enough of them or their ammo to go around.
so lots of boots end up pulling point defense with the old 5.56 saw or a couple m16s.
of course a 50 m2 would be better-- like everything else we just didn't have enough of them either.
a lot of the war is supply and demand. you have to fight with what you got or can get.
sometimes we would set up tangos/al-quaidas LMGs when we were lucky enough to have some fall into our hands that were still good.