I'm pretty much posting this question wherever I go to get the broadest base of responses. Here is my wild-ass idea: I have a SA loaded in .45. I'm researching the idea of getting a 9mm topend to use with my frame so I have two guns in one. Just to add more frivolity, suppose I have two different 9mm barrels and have one reamed to 9x23? Why couldn't I do all this?