This mission was added in version 9.2 (suggested by ian). This mission allows your whole team to get two additional weapons of your choice upon spawning for 10 minutes or until someone else makes a new deal. To start the mission, go to the Arms Dealer zone, and enter the checkpoint in-front of the old house, under the (Gun Icon) on the minimap.
You are now supposed to deliver the ammo box given by the Arms Dealer to your base. Once inside your base you need to finish the deal by typing /deal and choosing the weapons. The weapons chosen will be given to members of your team when they spawn. The whole deal expires after 10 minutes of dealing or when another team makes a new deal.