Aim for their crotches!
Aks any police officer if body armor will stop a shot from a 300 win mag-a common hunting rifle. Or a 7MM Remington mag, or a 30-06. 308, and on and on.
It wont.
Good pic to size them up.
Unless you have LAP ammo (Light Armor Piercing) best aim for the legs. Leg wounds remove people from the fight, create panic, screams, and need to get the wounded out.
Body Armor shouldnt be that hard to over come.