there are patents for the basic technology to use smokeless powder in the cylinder and still load like a traditional bp revolver.
However at this moment this patent is only in reference to the construction of a cylinder that allows the user to use 209 primers on the back. however smokeless powder is not mentioned in that patent, but it would techinically work with trailboss.
however, in america when we do a nitro proofed conversion on a bp revolver, we buy a cartridge conversion and load metal cases with smokeless propellants. that is all.