I know this will sound like a really silly question but here goes. Saw in another forum talk about the new S&W Shield in 9mm/.40 Cal. One comment was that he was going to buy a .40 and then only needed a 9mm Barrell and magazine to fire 9mm thru it. I've been debating on whether to get a .40 P30L or 9mm for a while - so this piqued my interest if at all possible for the same weapon models but with different calibers. I expect it could not be done due to differences in the recoil spring, slide tolerances, extractor etc. I've been an avid reader of the HK forum and if this was indeed possible I'm sure it would have been covered in here. Though a long shot I had to ask since it definitely would be nice to have two calibers for my P30 as well as future P30L almost for the price of one. If it sounds too good to be possibly true ....... ......