This must be done on a Majestic map. I personally accomplished this on Skyline FFA.
This one is much easier than it sounds, except for needing an ordnance drop to obtain the SAW (also possible to get this with the initial weapon spawns in the team mode). I paired it with the "Clever Girl" achievement. While hiding with Active Camo active it is very easy to get the jump on people. As soon as they run past you just start unloading into them. In the Majestic maps there are many areas with tunnels and stairways. Simply camp like a noob in these areas and as soon as you see someone on your radar, flip Active Camo on and go to town on your prey.
(Majestic DLC is no longer a gametype, so you will have to get lucky in match making and find a map this will work in)
EDIT: According to Solario32 "As of 2/19/15, playing just one or two Majestic maps will automatically pop all of the Majestic DLC achievements."