Mordecai won a chest full of guns in Moxxi’s Underdome a few years ago, but it was stolen by a thief named Carson. He says that Carson can be found in The Dust, and is actually found in Goose’s Roost, the area only accessible by jumping off of the big ramp that you did before during Too Close for Missiles. Fight through the entire camp and you’ll find Carson’s body underneath some metal in a lower area.

View Full-size

You'll need to boost your way off the giant rock (left) to get to Goose's Roost. The body you're looking for is under some metal on the opposite end of the entrance (right).

It turns out that was Carson’s brother, Mavis, underneath the metal and Carson was likely imprisoned at Friendship Gulag. If you’ve never been here before, you will be fighting through Loaders, Surveyors and Hyperion Personnel. Carson is being held at the back and when you get to him, you find out he’s dead. Pry open the two bars and grab his ECHO to find out the stash has been buried in The Dust.

Head back there and go to Ellie’s garage, taking the other path to Bug Gulch. This area is filled with Spiderants, so watch out and aim for their abdomens. Eventually, you’ll reach a hill, so take it and you’ll come to Boot Hill, which is where the stash is located. Dig up the graves until you find the chest and Mobley and Gettle will both appear. Kill them both and open the stash to finish the mission.