I'm having difficulty concealing my G19; I'm a thinner guy that doesn't wear oversized clothing. I'm considering a G26 but a friend at the local gun shop brought up the idea of the 40-9 (and 357) conversion for the G27. Sounds like a great idea on the surface; 3 guns for the price of one (plus barrels). I would most likely do the conversion so I can carry my G19 mags as backup. Plus 9mm ammo is cheaper than .40 and .357. This also gives me the option of have multiple calibers if the price of 9mm were to go above .40.
My question is (if you haven't already figured it out from the title), how reliable are those conversions? I understand the barrel is an easy swap. Would the .40 extractor be reliable with a 9mm round? And what about the magazines loading a 9mm round in a frame expecting a .40?