The salesman inside the dumpster will ask for food to be inserted into the dumpster via a small slot. In return a weapon is dispensed out.
The Army Surplus Fortress sells high-tier weapons with no special requirements, unlike the Mobile Gun Show, but for prices higher than other Traders offer. It is also the only Trader that sells Grenades.
Each item offered can only be purchased once.
Unlike most Traders, he will not give anything free if you don't have enough food.
The Group finds a dumpster. It's locked tight, with a slot in the side. There are weapon names and prices scrawled near the hole.
Just drop the food in here! says a tiny voice in the dumpster.