While it doesn't come up much as a game mode on this map CTF is a great way to get this achievement.
Focus on defense of your teams flag and kill the enemies that come to get it. Hide in corners of flag rooms with a weapon you're comfortable with, I used the EVA-8 Shotgun, and pick them off as they come in.
Another tip for this is to use Satchel Charges with the Dead Man Trigger if you have it. Drop them on the flag and if the enemy takes you out the charge should get them.
I've done this twice and got 13 kills the first time and 18 the next.