Kids' Rules are:
1. Cease!
2. Refrain from touching!
3. Get Out of There.
4. Speak with an Adult.
No, black powder is not nearly as potent as smokeless powder.
Unless you obtain a concealed weapons permit, it is prohibited.
Compared to black powder, smokeless powder has far greater potency. Smokeless powder makes it easy to blow up any muzzleloader.
Gun transfers in California must be carried out through a licensed California dealer where neither party to the transaction is a licensed guns dealer.
Shotguns have chokes, not shotgun shells.