Guys, I am getting interested in Sigs, and I have a few questions: 1) Are the calibers interchangeable between 9mm, 40 S&W, and 357 Sig? That is, can I just change barrels and mags? 2) Which 9mm models are available in SAO? 3) Which models are approximately a G19 size, but more narrow? That's all for now, but I'm sure I'll have more questions. Thanks, all!