Every single one of my rifles are SHTF rifles. Cause if the SHTF, my old a$$ is heading for the hills. I have 3 AR's, 1 AR10 in 7mm-08, 2 AR15's in 6.8spcII and .458SOCOM. they are my "Hogs and Dogs" rifles. (Coyote and Hogs). And if by some stupid twist of fate I ever had to use any for "combat" I am sure the 2 15's would suffice quite well.
Nomercy has given you great advice that I couldn't expand on if I wanted to. I've seen a few of the rifles he has built over the years and he knows his stuff better than a lot of other folks. As far as CQB goes, thats what my .45's and 9mm's are for