One of the informants gave you a note that was found near a dead adventurer:
"I've hidden some ammo in an old building where I found shelter for some nights. That's a good place - few know about it, and the terrain will keep others from getting it.."
[Once you've found your way to the inside of the building, you have to search for an ammobox. It contains a logbook and some swag. Please trade only equal, higher or not at all.]
If you're looking for the cache keep in mind that the terrain is rated 4! Watch out for fragile wood and always keep a tight grip, I don't want anyone to get hurt while doing this cache.
Everything on your own risk!