Howitzer Shells

In Boneyard's scavengers camp - the respawn location near Boneyard - talk to the Sergeant and ask him about the howitzer right next to him. He will complain about the lack of ammunition for it, and ask you to convince their producer to give them more. Jargo is the one to talk to, as he is Adytum's gunsmith. Convince him to produce more howitzer shells, and you will get the reward.