If you are nearing the end of the Tashgar mission and do not have enough points for this achievement, fear not. There is a spot at the end where enemies respawn infinitely allowing you to get the last points you need. Stock up on ammo while in the dam setting charges at every opportunity because there is no place to get more ammo at the infinite respawn. You don't need to take a sniper rifle in the end because the enemies are close enough that you can get headshots with an assault rifle or carbine. When you get to the end of the mission and are told to blow up the dam...DON'T. 3 enemies will infinitely respawn behind you above where you made the last jump. You will know you're in the right spot because your teammates will keep telling you to blow up the dam. Once you see the achievement pop, blow it up and end the mission.

If you need any help feel free to PM me.