I have used Lone Wolf barrels in my Glock's, since the 90's. They all have been "drop in", (no fitting required). My G 27, 40 S & W, works reliably with the 9 mm barrel. Long a I use, a 9 mm specific magazine. Only problem I have run across. Is that some of the 147 grain JHP's, with the blunt noses will have FTF jambs.