This weapon can be acquired from a gun rack in the Kite Bros Railway. (Requires Bolt Cutters)
High-Grade Gunpowder x Gunpowder
You’ll be able to acquire this attachment by placing two jewels into the machine in the Subway Safe Room
This attachment can be picked from a shelf in Kendo’s Gun Shop.
This attachment can be found hiding in a case at the Underground Storage.
Once you’ve progressed through the Downtown section of the game and acquired the Bolt Cutters. Head over to the Kite Bros Railway building and break open the gun rack to acquire the shotgun. This gun requires shotgun shells to use and is extreamly useful against the Hunter-y in the Sewers.