Im planning on getting the M&P next month and couldnt deciede on .40 or 9mm. I currently EDC a 9mm and a buddy of mine said stick to the same caliber for ammo, saving money etc... BUT I recently discovered that there are conversion barrels to take the .40 to a 9mm or even .357. So barrel plus new mags be looking at roughly $200 and you pretty much have two guns now! Anyone have any experience with this???