That "waffle" magazine is just ever so nifty! Those old 20" 1-12" twist barrels usually shoot quite well, chrome lining and all, just don't sling it up tight.
This is about as fancy as I care to go with an AR carbine, but it's "only" 8 lbs (and TOO much money!). But it's capable of quick hits to 500m :
But it's just hard to beat light and simple!
6 lbs, maybe 5lb 14 oz., with night sights.