No need. Bulletproof vests are no match for run-of-the-mill centerfire rifle rounds. Nor are kevlar helmets. So, unless they have rifle plates, center mass with the AR and whatever ammo you have will get it done, If they have plates, center mass to get them down, then head shots when they aren't moving.
You are correct to a point. We actually do have bulletproof vests that can withstand 6 AK47 rounds at 10-12 feet. We have had them since 2007ish...