The easiest way I found to get this achievement is to play on "Nuk3town" (It's a DLC map) during double experience points weekend. To find the map, go to multiplayer, bonus, and the click on "Nuk3town". I was able to get between 20-40k per game, and if your team wins then you get even more points. It should take you about 10 hours or less to get the achievement if you are playing during double experience points.
The Nuk3town is a bonus multiplayer map that comes with new copy of the game. If you got the game used then it might not be included. I included a video if you are not familiar with the map.