I am going to venture out a bit and put a pure opinion out.
I have been looking at Powders, 3F Goes F looks a lot like Pydro RS which is labeled as 2F.
777 3F is really fine compared to Pyro P which is 3F.
I was very careful to get 3F when I first started shooting. However, it was 777. No damage as I sent fairly low due to the reports of its energy density (aka more kaboom per measure).
In other words, as long as you keep the loads the same and or sane, I don't see there being any issue with 4F. People are saying 2F works great in BP revolvers. I got some, it works though some issues with load level and delayed kaboom (maybe more powder and a better kaboom, the velocity is pretty low, some chambers 550 fps).
For sure do not shoot 777.
I don't know reasonable loads would have any affect on a brass frame (modern). Metallurgy is vastly better. It would be interesting to see the loading manual for that type gun. Some old one I saw just said fill the chamber and compact the powder with the rammer.