I standardized on .357/.38 sp because I was able to find somebody selling two Ruger Vaqueros in that caliber very cheap . . . got a little Rossi Win '92 to match. Light and handy and of course zero recoil in that caliber.
We also cast and load our own Cowboy loads . . . we don't go so far as to use mouse f**t loads like so many 'gamers' do, in fact hubby loads his with considerable punch, but given the strict velocity rules we just roll our own.
We really need to get out of the suburbs, our neighbors already thought we were crazy, what with the dog agility equipment, the retriever blinds and wingers, and the horse jumps being constructed in the front yard . . . but when we got out the turkey fryer and started melting wheelweights in an old bar sink in the driveway . . . .
It is amazing how much lead you can get downrange and how quickly, with enough practice, even in the old single action revolvers and lever action rifles.
You should look at getting a production pot and click here for a great source for bullet alloys. Otherwise watch out for those pesky surveillance cameras in the Walmart parking when collecting wheel weights! ;-)