Diablo pistol thoughts

Doe's this pistol/shotgun meet ATF laws? If so what kind of shot shell would you shoot?

I have a bonds arms .45/.410 that is a handful with a .410 shell or .45 colt. i can load it down and it's fine. A 12 or 20 in the diablo seems like a handful and them some.

It is a muzzle loader that 7ses 209 primers.

Thanks. It was a pop up I saw. Didn't really check into it.