Out of Ammo achievements

Assist 20 enemy casualties

Kill 5 units with a single rocket

Beat the Sniper Challenge Mission

Beat Wave 20 on the Desert Mission

Beat Wave 20 on the Port Mission

Beat the Penthouse Challenge Mission

Beat the Plane Crash Challenge Mission

Survive for 30 minutes in a single round

Beat Wave 20 on the Forest Mission

Complete the Tutorial

10 kills while using a machine gun emplacement

2 kills while possessing a medic or engineer