Here's a homemade black powder volley gun that really works!

Shooting the 32 Barrel Machinegun

http://www.youtube.com/watch?v=cbvbLCs7iJ4

Here's a thread including photos and posts by the owner giving some background about it.
Notice that it even has a front & rear sight.

http://www.go2gbo.com/forums/index.php?topic=177367.0