I have a Ruger Blackhawk 357/9mm convertible and I highly recommend the Blackhawk convertible or plain one cylinder one for that matter. For target shooting it is pretty nice
Most gravatate to the Vaquero's after the Blackhawk. I also have a Ruger single 6 22lr/22 mag convertible and can't recommend Ruger single actions enough. For the price and quality they are hard to beat and like mentioned used blackhawks are also easy to find.
So shooting the 9mm doesn't harm the grooves in the barrel of a 357?