Excel Arms expands its X-Series line of pistol-caliber carbines with the X-5.7R. This semi-auto rifle chambered for 57 x 28mm utilizes the popular FN Five-Seven magazine available in 20- or 10-round capacity. The X-5.7R has both a top and bottom Picatinny rail for mounting various optics and accessories. It has an O.A. length of...