Achivement not registering

Hey, I'm trying to do the achivement where you don't shoot a single bullet from your main and support weapons in difficulty hard and above. However, I tried 2 times in public session, where I wasn't the Host, and it wasn't registered for either, and I'm sure I didn't shot a single bullet from my main and support weapons. Do I need all player to not shoot from main/support ? Do I need to host the game ? Or is it just broken ?