As much as I would like to think that is possible for the protection of the peoples constitutional security, no way. Well, unless all those civies were former soldiers themselves. The Infantry and Marines practice maneuver warfare to perfection and at the first shot the civies I am afraid to say would get fixed and rolled up in a heart beat. It would take some serious skill and dicipline in squad level tactics on the civies part to survive the first contact. Sure you could plink "joe" that is half-stepping with your ACOG all day long, but you would need to be worrying about the other platoon/squad/fire team that is flanking while you were doing it.
You guys dreaming of SHTF scenarios like that should practice and learn to perfection the battle drills of FM 7-8 Infantry Rifle Platoon & Squad at the very minimum.
FM 7-8 Site