Can be done quite easily all you need is 2 gamers wanting this. Just keep trading kills until one person gets it then repeat for the other person. It will take a while but if you have someone to boost this game with it should only take about 2 hours max for both of you to get it. Also this goes toward the the 500 multiplay kills. (the 2 hours is based on how fast you can kill each other its also helpful to boost for other ranked achievements while you are getting these kills)