"Open gun shipment" is an objective in the quest Get Frosty in How Marcus Saved Mercenary Day DLC
Walkthrough[edit]
Head back into Gingerton from On Frozen Pond. Go to the front of the Mercenary Day Tree and the train willpull up. Pull the lever to reveal the massive chests of goodies that Marcus is offering to you. Grab what you want then talk with Smaller Timmy to complete the quest.
