I think it really depends on what cartridge you're trying to fire in your S&W. Ranch Products (or a name very like that) in Malinta, Ohio make all sorts of moon clips. Whatever cartridge you want to use, best check the manuals to make sure the bullet diameter isn't too large, or you'll wear your pistols barrel faster than you'll want to. The 9mm is about .355 and so wouldn't be a problem in a .357 barrel, but there are a lot of 9mm cartridges and a good deal of variation in them. Nice idea, and good luck with it.