It could possibly be converted to a .45/70-type BP ctg. The rebounding hammers usually are not capable of allowing higher pressure ammunition, but some are. This Russian gun may or may not possess the strength to allow for re-tubing on the monoblock to a smokeless-type round, certainly nothing like a nitro-express round. This 'work' will cost you much more than the end result will be worth, unless you can do much of the work yourself. I suggest you find something else to 'play' with.
; Most shotguns are designed around handling pressure up to 12,000psi, which is the maximum allowed in shotgun ammunition. Some are over-built, allowing for transformation, while others should be left as shotguns.
: Since most Russian guns have chrome lined bores, rifling those present would not be a possibiltiy. If non-chrome lined bores were present, they could possilby be rifled, then you would have a powerful BP 12 bore rifle, however the spread of the bores at the breech is usually too much to allow the bores to shoot together, but handloading possibly would allow this to work - of course, if not chrome lined.