Sig Sauer MCX Stock Adapter Kit - SKU: 2401191-R - UPC: 798681581207
Product Description
The Sig Sauer MCX Stock Adapter Kit (2401191-R) is a factory OEM conversion kit engineered to adapt standard AR-15 lower receivers to accept Sig Sauer MCX, MPX, or 1913 Picatinny rail-mounted folding and telescoping stock assemblies. Designed for shooters building custom SIG MCX upper receiver conversions on legacy lower receiver platforms, this adapter converts the standard threaded buffer tube receiver extension interface into a vertical M1913 Picatinny rail section.
Precision-machined from high-strength aircraft aluminum and finished in a durable matte black hardcoat anodize, the 2401191-R kit seamlessly threads into any standard 1-3/16"-16 UN AR-15 receiver buffer tube threads. The kit features a lower receiver rear plate plug that securely captures the rear takedown pin spring and detent while providing a rock-solid, anti-rotation seat for the Picatinny rail adapter block.
Whether staging an MCX Virtus, SPEAR LT, or MPX upper assembly on a Mil-Spec AR lower, the Sig Sauer 2401191-R Stock Adapter Kit delivers factory-tier fitment, zero-play lockup, and seamless integration for modern side-folding stock and brace setups.
*Armorer Bench Notes & Real-World Staging Guidance:
Fitment Matrix: Direct fit for all standard Mil-Spec AR-15 lower receivers. Allows installation of MCX/MPX Picatinny-mounted stocks and braces.
- Verify host AR lower receiver is completely clear, magazine removed, safety engaged, and workspace clean.
- Remove existing buffer tube, buffer, spring, endplate, and castle nut, ensuring rear takedown pin detent and spring are retained.
- Thread the receiver adapter insert clockwise into the buffer tube threads of the lower receiver.
- Seat the lower receiver plug/plate over the rear receiver face, ensuring the takedown pin spring is compressed properly without binding.
- Tighten the central adapter tension bolt to 30–35 in-lbs using a hex driver, verifying full flush alignment and zero rotation before mounting Picatinny stock accessories.
Key Features
- Factory Sig Sauer OEM Quality: Guarantees perfect dimensional tolerance and lockup with MCX/MPX factory stocks and braces.
- AR-15 to 1913 Rail Conversion: Converts standard threaded AR-15 receiver buffer threads to a vertical M1913 Picatinny interface.
- Aircraft-Grade Aluminum Build: Lightweight, ultra-durable alloy housing withstands heavy recoil and side-folding lockup stress.
- Integrated Takedown Spring Capture: Custom backing plate holds the rear takedown pin detent and spring securely in place.
- Matte Black Anodized Finish: Hardcoat anodizing offers chemical, scratch, and environmental corrosion resistance.
- Anti-Rotation Design: Internal tensioning system prevents the adapter block from loosening under hard operational use.
Product Specifications
- Brand: Sig Sauer
- Model: MCX Stock Adapter Kit
- MPN: 2401191-R / 2401191R
- SKU: 2401191-R
- UPC: 798681581207
- Platform Compatibility: Standard Mil-Spec AR-15 Lower Receivers
- Interface Style: Threaded Receiver to Vertical M1913 Picatinny Rail
- Material: Aircraft-Grade Aluminum / Steel Hardware
- Finish/Color: Matte Black Hardcoat Anodized
- Country of Origin: USA
