This guide shows how to find the Black Powder Rifle. (Unique Weapon)
Black Powder Rifle Stats
Black Powder Rifle Location
The location is not far from Palace of the Winding Path and Philippi Battlefield Cemetery.
Inside the house you can find the Black Powder Rifle. The weapon spawns in random cabinets. If there is no rifle, you must log off and enter the game again.
Have fun!