Addressing the elephant in the room, it compares well to the Glock 43. In fact, it is just slightly shorter. They share the same standard magazine capacity, but the FN-made gun comes with steel rather than plastic sights. Glock s single-stack 9mm runs 6.26 inches overall due to a 3.41-inch barrel. However, the G43 is a hair shorter than the FN 503, which stands 4.25 inches tall with a flush-fit 6-shot mag inserted. FN 503 s included extended 8-shot mag with a grip sleeve adds about an inch to the height. It is an apples-to-apples comparison to the G43 with aftermarket tactical mag extensions. Gratefully, FN ships the 503 with one magazine of each length.