For what its worth, both of my buddies that carry the 340PD do NOT carry it with .357! They are smart enough to stick with .38+P in their little demon's! Before I got my 442 I carried a 360J which is a scandium .38 special gun but still a steel cylinder. S&W will actually put a .357 cylinder if you like or if you are mentally deranged. Pretty much all the airweight J-frame's will deliver more than enough "equal and opposite reaction" to your meat mittens with warm .38's let alone .357 of any flavor. There is no doubt that you get a fair step up performance with .357 but I would rather have a more mildly recoiling gun that is easier to hit with and probably faster.