Here is the full list of all 12 Harms Way achievements worth 200 gamerscore. It takes around 1-2 hours to unlock all of the achievements on Xbox 360.
Join a multiplayer game for the first time
Just look at credits
Activate a turret downgrade powerup
Deploy mines for the first time
Shoot and takeover an enemy turret
Get the missile launcher for the first time
Host a multiplayer game for the first time
Wreck an opponent as a shooter
Hit the windshield of a driver
Win a game in Single Player
Hit the tires of a driver
Wreck your vehicle