My first thought about "armored bad guys" was maybe I should spend $199 on a CZ-52 in 7.62x25 Tok! That's a fast, hot round, but the risk of overpenetration, ricochets, etc make it less than desireable.
If I shoot someone 2 or 3 times COM and he's not going down for the count, my point of aim is going to shift. Either low, to the hips/groin/gonads region or to the head & neck. Presuming that those targets are too hard to hit, I'll keep putting them COM - with the idea that someone absorbing between 5 to 8 impacts of 250 to 450 ft-lbs over the sternum & ribs will get the hint that I don't play well with others.
I'll take "targets of opportunity" if I can (if I'm not shaking so bad I can't aim), like knees, ankles, hands & arms which are seldom shielded.
BillCA in CA (Unfortunately)