Powder: Any black powder FFFg (recommended to use black powder), you can also use Pyrodex P or Triple 7 (FFF grade is best). Available at most gun shops and sporting goods stores. You can also use crushed matchheads or powder from fireworks such as blackcats.
Ammunition: .30 Caliber which is 5/16" slingshot steel ball ammo. Available at most outdoor stores such as Academy or online at eBay.com
Fuse: Any Fireworks Fuse 1.8mm or 1/16" diameter or smaller, blackcat fuses will also work.