An advanced Tactical Stock System for the Remington 870 12 gauge shotgun, utilizing a proprietary, lightweight, carbon-fiber reinforced polymer. A six-position, collapsible butt-stock allows shot-gunners of all sizes to find the optimum adjustment for fit and comfort. The military-length forend can be configured with a smooth fore-cap, or with a mini tri-rail cap to allow the mounting of Picatinny rail-mount accessories without sacrificing comfort or convenience. A 7 round shell carrier mounts to the left side of the receiver and includes individual shell-retention adjustment for each round, without interfering with the stroke of the forend. For Remington 870 12 Gauge shotguns only.