Boom J,
Yes, that's how it works. 18" threaded 22 cal barrels are screwed into the bronze piece at the front and tied together with a ring at the muzzle end. A 'tiller' with a grip on it is screwed into the rear of the tripod mount to aim it. The 'chambers' are shaped like a 45 ACP round to fit the modified mag. It works well, and IIRC will fire ~300 round/minute.
I originally built it as a prototype, thinking it was something new that might be patentable (this was in pre-internet days). Then I found out about Dardick.
I never thought of using a similar design for black powder until seeing Dom's one here. If the parts to make it feed and fire with firing pins were deleted, it would be fairly simple to make a BP one.
Here's what the internals look like...
This is a 38 cal Tround...
Maybe Dom could make me a golf-ball one.