This is a storyline achievement which can be achieved in Mombasa Streets. However, if, like me, you decided to just use level select to choose what missions to play, then you can miss this achievement.
To get this achievement, load up Mombasa Streets with Rally Point 3 (Gauss Turret), and follow VISR directions to get to the Gauss Turret, and then pick it up by holding
. This will award you this achievement.
If you get lost or go into a dead end, you can get helpful directions from your VISR by pressing either
to get an 'emoticon' target locator to appear.
The Gauss Turret is located on the balcony of a building overlooking the area where the beacon is on your VISR map. You'll have to go up a few sets of stairs to get it.