This can be boosted, you only need 4 people to start a match of Drop Zone. Set your matchmaking to Asia, and try to equip the Scatter Gun, this will make it easier as the window of opportunity to get these kills is very small. You need to kill someone while they are trying to claim a drop pod you have already claimed and is counting down. The Scatter Gun, Scout Pistol and Cycler Rifle work best for the instant kill.
You'll know it counts if when you see a display upon a kill that says you stopped the capture. For security, check your Achievement tracking in the Xbox Guide.