Yeah, it's really difficult.

Normally, that is. But you can get achievement credit if you do expert campaigns in mutations as well.

And the mutation this week gives everyone a M60 machine gun - one of the highest damage guns in game - with unlimited ammo.

So, anyone want to rack up some expert campaign completions?

Some tips on this achievement here:
http://www.trueachievements.com/achi...vementid=38554

My steam page can be found here: http://steamcommunity.com/profiles/7...000630449/home (you'll need to log in and then reenter the URL), and my user name is Crazed_Rabbit.

CR