The old originals shot blackpowder just fine.
If they were finicky - the Army wouldn't've wanted another production run, but by the time they did, S&W was too invested in commercial sales, and declined.
These new revolvers were specifically designed for smokeless powder and wonder of wonders - they all shoot that propellant admirably.
Plus - today, these new guns are being used as sporting toys rather than as weapons - so they're receiving far more 'play' than any of the originals were ever subjected to throughout their service life.
The Army simply did not practice 'Handgun Marksmanship' as it's done today - there wasn't much money allocated for the ammunition, and the primary weapon was the Carbine for the Cavalryman, or Rifle, if in an Infantry outfit.
From a gunsmithing standpoint - shortening a cylinder and adding a bushing/washer will necessitate a corresponding lengthening of the barrel into the frame for cylinder-to-forcing cone gap, and if you think you've got a powder fouling problem now - see what there'll be for build-up if that issue isn't addressed.
The problems 'may' lie in the use of substitute blackpowder - but I can't say, since every Italian-made clone seems to be different, when it comes to tolerances and metallurgy.
Vaya,
Scouts Out!