Fast Shooter

Strategy - Open the gate to the Stingray Facility, engage the NPC's near the gate and run to the end with a rocket launcher to kill the lil' scavs before they close the gate. The gate is at the far end of the facility. The mobs must be engaged at the beginning near the gate you open for the lil' scavs to spawn at the far end.

NOTE: If you fail this and reach the end of this zone to complete the main objective of the quest, you don't get another chance. (Best you reload if the challenge isn't met)