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Sig Sauer MCX-SPEAR LT 5.56/300BLK Bolt Carrier Assembly 8901280 UPC 391617924934
Product Description
The Sig Sauer 8901280 is an authentic factory OEM replacement complete bolt carrier assembly engineered specifically for the MCX-SPEAR LT platform chambered in 5.56x45mm NATO and .300 AAC Blackout. Manufactured to exact military-grade specifications, this complete assembly includes the carrier, dual recoil spring recoil system, firing pin, firing pin latch, cam pin, and multi-lug bolt assembly. Precision-machined from high-grade steel alloys and coated with a protective wear-resistant finish, this carrier assembly delivers consistent lockup, extraction, and cycling under high-tempo firing schedules.
Designed for the short-stroke gas piston architecture of the MCX-SPEAR LT series, this assembly features integrated dual captive recoil springs mounted directly to the upper carriage. This self-contained recoil design eliminates the requirement for a traditional AR-15 buffer tube and buffer assembly, allowing the host firearm to utilize folding stock configurations while firing seamlessly. The multi-lug bolt head is high-pressure tested (HPT) and magnetic particle inspected (MPI) to prevent fatigue failures and withstand extreme chamber pressures associated with suppressed .300 Blackout subsonic and high-velocity 5.56 NATO loads.
Whether servicing a high-round-count duty rifle or keeping a mission-critical spare in field gear, this drop-in factory replacement preserves factory warranty standards and original operating tolerances. It provides seamless function across all MCX-SPEAR LT 5.56 and .300BLK upper receiver variants while maintaining reverse compatibility with earlier MCX Virtus uppers when utilizing the appropriate firing pin latch configuration.
Armorer Bench Notes & Real-World Staging Guidance:
Fitment Matrix: Fits Sig Sauer MCX-SPEAR LT upper receivers chambered in 5.56 NATO and .300 AAC Blackout natively. Compatible with MCX Virtus 5.56/300BLK uppers. Not compatible with MCX-SPEAR Large Frame (7.62x51 / .277 Fury) or standard AR-15 direct-impingement receivers.
- Confirm the host firearm is completely clear: remove the magazine, lock the action back, and visually and physically inspect the chamber to ensure it is unloaded.
- Push out the rear receiver takedown pin and pivot the upper receiver open from the lower receiver assembly.
- Grasp the rear carriage of the recoil spring guide rod assembly and slide the complete carrier assembly out from the rear of the upper receiver.
- Lightly coat the carrier slide rails, bolt lugs, cam pin slot, and dual guide rods with high-grade synthetic weapon grease or oil.
- Align the bolt carrier assembly with the upper receiver track and slide forward until the bolt seats fully into the barrel extension.
- Close the upper receiver, push in the takedown pin, and cycle the charging handle manually to perform a dry-fire function test and verify proper bolt lockup, trigger reset, and smooth recoil spring travel.
Key Features
- Factory OEM Sig Sauer Construction: Genuine OEM replacement part ensures precise fitment, factory reliability, and strict tolerance adherence.
- Self-Contained Dual Recoil Spring System: Integrated guide rods and captive spring assembly eliminate the traditional buffer tube for side-folding stock functionality.
- Multi-Caliber Compatibility: Serves as a direct drop-in replacement for both 5.56x45mm NATO and .300 AAC Blackout MCX-SPEAR LT configurations.
- HPT / MPI Inspected Bolt: Bolt head is High Pressure Tested and Magnetic Particle Inspected to guarantee structural integrity under extreme firing stress.
- Advanced Surface Coating: Protective matte finish reduces friction, eases carbon fouling removal, and shields against environmental corrosion.
- Complete Drop-In Assembly: Ships fully assembled with carrier, bolt, firing pin, cam pin, and captive recoil spring assembly for instant field replacement.
Product Specifications
- Brand: Sig Sauer
- Model/Series: MCX-SPEAR LT Bolt Carrier Assembly
- MPN / SKU: 8901280
- UPC: 391617924934
- Caliber Compatibility: 5.56x45mm NATO / .300 AAC Blackout
- Platform Fitment: Sig Sauer MCX-SPEAR LT, MCX Virtus
- Material: High-Grade Heat-Treated Steel
- Finish: Matte Black / Wear-Resistant Coating
- Includes: Carrier, Bolt Assembly, Firing Pin, Cam Pin, Captive Dual Recoil Springs
- Country of Origin: USA
