Skeet ShooterG 10

You can grind this out in local multiplayer with 2 controllers. I suggest changing the weapons to sniper rifles and altering the game settings to remove shields so everything is a one hit kill.

Load up the Bloodline map (Coagulation/Blood Gulch) and position the player getting the achievement in the center of the map. Move the dummy account to the roof of the nearest base, make sure the other player is looking in the right direction, and move the dummy into the man cannon. Then, shoot the dummy out of the air with your primary account.

It may take a few tries to get the hang of it, but once you get the kill, repeat the process 14 more times.

If you’re still having trouble you can position the dummy right in front of the man cannon and use your foot to walk it forward the last few steps, that way you can have both hands on the controller for your primary account.