A lighting device is mountable on the side of an automatic pistol by using openings already formed in the pistol body to connect the pistol body to the frame rail of the pistol using frame insert pins. In a retrofit application, to connect the lighting device to the pistol, the frame insert pins are removed from the pistol, the lighting device is aligned with the side of the pistol such that one or more apertures of the lighting device align with an opening in which the frame insert pin(s) were removed, and either the same frame insert pins, or slightly longer ones, are inserted through the aligned apertures and openings. In this manner, the lighting device is mounted to a side of the body of the pistol, and the side portion of the body of the pistol is again connected to the frame rail.