A method of modifying a .45 ACP pistol having a slide and a receiver defining a magazine well includes the steps of reducing the size of the magazine well and shortening the slide. The slide includes a breech face and a proximal end and the magazine well includes a front wall and spaced therefrom a rear wall. Reducing the size of the magazine well involves moving the rear wall closer to the front wall. Shortening the slide involves removing material from between the breech face and the proximal end. The shortening of the slide generally corresponds to the size reduction of the magazine well.