While calculating cost, don't forget about the much higher price of .38/.357 moonclips and the costs of the specific brass you will need to fit them, someone else can explain that better and there are threads-a-plenty on it. In the 625 Ranch moons, $35 per 100, and mixed range brass has worked well for me. FWIW the only local guy that consistently bests me in the revolver divisions shoots a 4" mooned 686.