This is your fairly standard achievement however to speed things up i suggest the following.
- Play the 'deathmatch' playlist which is basically a free-for-all game mode; if you get used to the shotgun/AR and jumping into battles you're going to get this pretty quick (took me 5 games)
- Using grenades is also very handy; throw them directly into players who are already engaged in fights and you may pick up 2-3 kills depending on your luck.
Either way play this game for an hour and you should have this.
Enjoy