The Raider brand BB gun is a small lever-action air rifle. The only thing this toy is practical for is killing radroaches.
This weapon's damage, critical damage, and item HP are all double that of a normal BB gun, and its value has been raised accordingly from 36 to 60 caps. In all other aspects it is identical to a normal BB gun.
This weapon can not be found anywhere in the game. It is obtainable only via console command on PC or inventory edit on Xbox 360. To get Black Bart's Bane, use the console command: player.additem 6B535 1
Behind the scenes
Its name is a reference to A Christmas Story. Ralphie, having just received his new BB gun, takes aim at a target across the yard and mumbles "Okay, Black Bart... now you get yours!"