Big Gun
From Project Nomads Unofficial Wiki
Obtaining
In chapter 1, part 4 "After the Storm", Travayne hands the player a red level 1 guntower along with a red Big Gun.
In chapter 1, part 5 "The Athanor", a red Big Gun is hidden behind an island, in front of the Bomber 3 garage.
In chapter 2, part 5 "The Store of Artifacts", a red Big Gun is available next to the Sentinel lighthouse.