Army of Two (EU)

Equip a machine gun and kill as many enemies as you can playing through the game.

Probably best to just buy the cheapest machine gun as soon as you get the achievement for having used the assault rifle, cos otherwise you are likely killing more enemies with the same gun that could better be used to work on this achievement.

The machine gun is a very powerful weapon, and thus will draw lots of aggro. The negative is that it can also be a bit more inaccurate.

100% works, Recruit difficulty, Single player or CO-OP

Weapons: Any Machine gun (I used SAW), RPG

Go onto level ''Aircraft Carrier'' and get to the section whereby you have to use the harrier to blow open a metal door. Use RPG to kill the heavy armour guy then turn left and run around the stationary missiles so your looking at the brightly lit opening.

Use your MG to kill the enemy. Can get up-to 9 kills depending on if you team mate gets the kills.

*Secondary achievement available* L'Abattoir (Read achievement description and the rest if obvious)