2. But now I've found a thread and 2 posts from thefiringline that I had previously posted about on thehighroad back in 2011.
These indicate that some TFL members have indeed openly admitted that they've loaded smokeless powder into their Ruger Old Army without a problem.
They used a booster charge of black powder to ignite the smokeless powder. --->>> https://www.thehighroad.org/index.php?threads/hypothetical-situation.570697/#post-7047942
The most relevant posts of the first thread listed are on page 2.
For those who weren't aware, thefiringline is often referred to as THR's sister site.
TFL's BP moderator 4v50 Gary is also the moderator of THR's BP forum.
You can use it but you won't be happy with the results. One of my Iron Rules I won't use smokeless even in black powder cartridge guns. Don't know what the Italian proof law are like-do they even have them, but I suspect the legal/accepted pressures for BP are way below smokeless.