Save at least three Big Earl rockets from the beginning of the game from M-4. When you go to the part where Hendrix first contacts you in the tunnel, after about 24 feet, you will reach the catwalk outside with the earthen bridge where the APC and convoy of troops are advancing toward the guard station. Fire one shot near the outer track (the one facing you). After the first shot, the APC will begin to buckle, and tilt down. Since that the track is stuck, fire another shot near the front of the vehicle, closest as possible without hitting the APC. Shoot the next shot again right outside of the outer track, further down from where the first rocket hit. In the process, you burrow a hole big enough for the APC to fall through and go sailing down to the bottom of the Chasm (watch it long enough and see the explosion); or the APC will be immobilized, creating a bit of an obstacle for the soldiers to go around, and provide a very good sniping position. The soldiers will most likely stay on their side of the hole, even if they can walk around it. Beware, as if the APC tilts less than 45 degrees inverted, the small mounted machine gun can still shoot at you -- try to get the front of the APC very deep into the hole you create by shooting it.