Yep, .40 is my favorite in a handgun caliber as well. I had a G23 first, then when I wanted a smaller one to carry I went with the G27 so I could stay with the same caliber of ammo. After I got it I found out that the 23 mags fit the 27 too so that was a bonus. They stick out the bottom a bit, but they work just fine. Also, they make a 'magazine sleeve' for the 23 mags.....it's a small plastic 'sleeve' that fits over the 23 mags and basically makes it look better when you use the bigger mags in the 27......you don't need the sleeve for them to work though. I carry my 27 with a regular mag and then I carry a mag from my 23 as a backup.....gives me 13 extra instead of 9.