XA-4 Series ERMOX XA-4 Tactical Semi-Automatic Shotgun features Auto-Regulating Gas-Operated (ARGO) system: a simple, self-cleaning, piston-driven action. The unique, short-stroke, dual-piston design has a gas ported located just forward of the chamber, resulting in less fouling and more reliable cycling. Pistons push directly against the bolt, for faster operation and minimal vibration. This eliminates any extra weight from any connecting linkages or heavy action bars under the forend. The result: Marine-tough reliability, for the harshest environments. A black synthetic collapsible stock features a textured pistol grip. The 18-1/2″ barrel includes an adjustable ghost ring rear sight, and fixed blade front sight, plus standard M choke tube. A picatinny rail awaits your optics (not included). The drilled and tapped receiver is ready for the elements, in an anodized black finish.