Staying on the subject of attempts to bypass Colt's revolver patent, let's go for an entire class of weapons people barely remember, the chain rifle:
Treeby Chain Rifle of 1855. Since the things on the belt are chambers rather than rounds, this is actually a belt-fed revolver. The big handle in front of the chambers was a screw thread for sealing the gap between the front of the chamber and the barrel, you had to turn it down to form a seal before the weapon would actually fire.
There were also handguns of this type.
1866 Josselyn 20-round chain revolver:
And this thing. Nobody's that sure what it is, but it's in Tula's small arms museum labelled as a prototype from the 1920s.
