So who are you going to be fighting? Probably not a trained army. Probably some BLM or Antifa jerks. They're gonna be scared if someone puts rounds on them. Under these circumstances, a fortification might work fine. I don't think they're gonna do fire and maneuver. In fact, when they hear the crack (sonic boom) of rounds going over their head or close, they'll probably remember they had an appointment on the other side of town.
As for where to shoot, won't a 30-06 penetrate a bullet proof vest? 30-06 152 grain ball ammo will penetrate 1/4 inch of steel. So shoot center of mass.
As for accuracy, I think 3 MOA is enough to hit humans at ranges up to 500 yards. Doubt if they'll be that far.
Almost any rifle made will shoot better than 3 MOA. So I would not worry about rifle accuracy, just effectiveness.
