http://www.smammo.com/5-56nato-223rem/ One of these into the gas tank of a vehicle and nobody will be using THAT vehicle to travel or for cover!
A few of them aimed at a chopper will make said chopper back off half a mile or so, too. Giving you time and space to get down a manhole, cover up with space blanket (nighttime). If they can't hover over you, they can't give real time info to the ground force. Without belt feds and rockets, they can't do anything to you from a chopper (that you need to worry about). It's much easier for you to hit that chopper (from cover) than it is for them to hit you (behind cover) You can hear/see that chopper from a long ways off, so cover IS going to be feasible for you.
Crap, the BOB just got a lb heavier
Crap, the BOB just got a lb heavier