I've had two Ruger convertibles over the years. IMHO, the 9MM/.357 is one of those ideas that really looks good on paper but doesn't work out all that well in practice.
When MilSurp 9MM was available dirt cheap, I used a lot of it in Rugers for informal, short range plinking, but it loses accuracy fast past about 15 yards. (At least, both of my guns did)
For pure Accuracy, my best results came with 148 gr hollow base full wadcutters, loaded in .357 cases over 3.2-3.5 grains of Bullseye.
My best all around load in these weapons was a Lyman 168 grain (linotype) cast (358-429??) over a MAX charge of H-110.
Surprisingly, my most accurate jacketed bullet load was the Remington 125 GR. JHP, again over a max charge of H110.