I think the patents on the Puckle have expired, so have fun. It is not a machinegun, or even a Gatling type, as the cylinder has to be manually rotated. Actually, it would be perfectly legal even with fixed ammunition, but would be a "firearm" like any manually operated rifle or shotgun. With flint or percussion, not firing fixed ammunition, it would not even be a gun.
As DZ says, the crank on the Puckle does not rotate the cylinder or fire the chamber, it turns on a screw to bring the chamber in against the end of the barrel and eliminate the barrel-cylinder gap seen in most modern revolvers. The Russian Nagant revolver uses a variation on the idea.