In revolvers I think 777 shoots very well and very clean. In your Ruger Old Army it should be pretty ideal. It's the best thing I've found so far for my Remington Navy .36.
I discovered that 777 compresses quite a bit, so not only is it hotter, but you can get much more of it in a revolver cylinder for a very powerful load.
In the Ruger, or my Remingtons, this is not an issue, but I also "discovered" that in the open top Colts a full load of 777 is just a bit too much. It will batter the wedge and wedge slot and definately drop the loading lever. "Don't ask me how I know this", to quote a friend of mine.