Army of Two Tips

Easy weapon achievements
Having trouble getting those weapon achievements? Doing multiple playthroughs? Worry no more. First go into the training mission. (start a new campaign) After Pedro Tells you Somthings gonna hurt tell your partner to advance. Throw a grenade at his feet so he jumps into the proximity mine. Grab him, drag him be hind the wall and start killing the enemies. Your partner will never die so just leave him on the ground. You are also Invincible and have unlimited ammo. Sounds too good to be true? Try it yourself. it works. ( if you need to use an SMG trade your partner to get a scorpion.)