Abstract: A first support ring is arranged for positioning about a forward threaded portion of a magazine tube to complementarily engage a bottom surface of the associated gun barrel, wherein a second ring is arranged for locked engagement with the first ring upon directing the associated magazine tube cap into abutting relationship with locking spheres mounted in a projecting relationship relative to the forward walls of the second support ring. A mounting plate is oriented between the butt stock and the butt pad of the associated shotgun, wherein a flexible sling member is arranged for securement between the second support ring having a mounting lug and the mounting plate having a mounting plate mounting lug extending beyond the respective second support ring and the mounting plate.