It will actually be easier to convert your G27 from 40S&W to the .357sig than either the G32 or G27 to 9mm. You should be able to use your 40S&W magazines for the .357sig and keep the stock ejector. If you're going from 40S&W or .357sig to 9mm, it's recommended to change the ejector. I haven't heard of many issues with conversion barrels in the 9mm, 40S&W, or .357sig. LWD barrels seem to be the most talked about, but there are a couple of other manufacturers. Strange coincidence........my wife and I will also be taking our Glock armorers course in February. I've been working on my own Glocks for ten years, and we plan on going into business commercially.