[AmericanChopper]

You pretty much had it right. It seems the two things you missed were:

1. Milling the powder makes it a lot more effective. My buddies and I would make ball mills with old washing machine engines, and whatever non-sparking material we could find for the balls.

2. If you want it to explode rather than burn you have to granulate it. Wet it and let it dry, and grind it a little bit and pass it through some mesh to grade it.

The raw powder is good for making rockets, but it won’t very readily explode.

[bserge]

Black powder won't detonate by it's nature, it just deflagrates, burns real fast. Those cartridges can hold a lot of pressure, only something with a higher explosive velocity like nitroglycerin or TNT can fragment them.