The SIG SAUER MCX-SPEAR LT 11.5" 5.56 NATO Complete Upper Assembly brings the advanced design and proven performance of the MCX platform to a modernized, adaptable configuration. Developed with input from the Special Forces community, the MCX-SPEAR LT platform is engineered for reliability, durability, accuracy, and modularity in demanding shooting environments.

Designed to adapt to an M4/AR-15 specification lower assembly, the MCX-SPEAR LT replaces the traditional buffer system with a dual-rod recoil assembly, allowing for folding stock compatibility while maintaining a compact and versatile platform. The included receiver extension delete stock adapter allows compatible folding or fixed stocks and braces using a vertical 1913 rail system to be installed.

This complete 11.5-inch upper assembly is chambered in 5.56 NATO and features a cold hammer forged barrel with a 1:7 twist rate. The gas piston operating system helps reduce exposure of critical components to carbon fouling, while the adjustable gas system allows users to optimize operation when using a suppressor. The quick-change barrel design provides additional versatility for changing barrel lengths and calibers within the MCX-SPEAR LT platform.

The free-floated aluminum handguard measures 10.23 inches and provides a stable platform for accessories. An included 3-prong SIG suppressor-ready QD flash hider features 1/2x28 muzzle threads and is designed for compatibility with SIG SAUER SLX and SLH suppressor systems utilizing the Clutch-LOK QD mounting system.

The MCX-SPEAR LT incorporates an ambidextrous charging handle with gas deflector and a tapered bolt design engineered for enhanced reliability and service life. Replaceable components—including the cam path follower, feed ramp, forward assist/deflector, and charging handle locking pins—are designed to help extend receiver service life compared with conventional AR-pattern designs.

The package includes the complete 11.5-inch 5.56 NATO upper assembly, SIG flip-up iron sights, removable 3-prong flash hider, and receiver extension delete stock adapter. With its piston-driven operating system, folding stock capability, modular barrel design, and robust construction, the SIG SAUER MCX-SPEAR LT delivers a modern and adaptable approach to the AR-pattern platform.

Key Features:

• SIG SAUER MCX-SPEAR LT complete upper assembly

• 5.56 NATO chambering

• 11.5-inch chrome lined barrel

• 1:7 twist rate

• M4/AR-15 specification lower compatibility

• Dual-rod recoil assembly

• Receiver extension delete design

• Folding stock and brace compatibility with vertical 1913 rail systems

• Gas piston operating system

• Adjustable gas system for suppressor optimization

• Quick-change barrel design

• Free-floated 10.23-inch aluminum handguard

• Ambidextrous charging handle with gas deflector

• Tapered bolt design

• DLC-finished bolt carrier

• 3-prong SIG suppressor-ready QD flash hider

• 1/2x28 muzzle thread pitch

• Compatible with SIG SLX and SLH suppressor systems

• SIG flip-up iron sights included

• Forward assist included

• Black anodized receiver finish

• Designed for extended service life and high round-count use