Bountyhunter,

The gun you are looking for already exists. The FN Baracuda is exactly that with interchangeable cylinder/crane assembly in 9mm/.357. You will pay a premium for one though. I think the main problem with such a gun is that ballistically there is nothing a 9mm will do for you that isn't found within the .38 special - .357 magnum envelope. I love the idea of versatility especially in a survival handgun. The .357 magnum has about the widest range of power of any of them from .38 wadcutters to heavy magnum loads. To throw 9mm into the mix you are just expanding the middle in terms of power. Mac