How to unlock: you will receive this quest from Desdemona once you finish Railroad's faction main plot (The Nuclear Option quest). It might not happen at your first visit to the Railroad H.Q (M6,2) after meeting the condition.
The quest consists of six parts. Go back to the Railroad H.Q. after completing the main plot. If you will see Patriot in the middle of the room, then Desdemona will give you mission objectives.
Each objective is about removing one of the gang leaders, usually surrounded by thugs. Not each of them is easily accessible, but very frequently it is possible to eliminate them from far away by using sniper rifle. Killing their backup isn't mandatory.
Quest rewards: 100-300 bottlecaps, occasionally a random weapon/armor part