Description
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SIG Sauer MCX-SPEAR LT 9″ 300BLK Upper AR Conversion Kit – FDE – UAMCX-300B-9B-LT-IR
The SIG Sauer MCX-SPEAR LT 9″ Upper Conversion Kit (UAMCX-300B-9B-LT-IR) is the ultimate 2026-spec upgrade for shooters looking to bring the revolutionary MCX-SPEAR LT platform to their standard AR-15 lower receiver. This kit features a 9-inch barrel chambered in the versatile .300 Blackout, optimized for suppressed performance and high-energy delivery from a compact footprint. The “LT” designation signifies the latest lightweight evolution of the MCX, featuring a redesigned handguard that offers improved rigidity for lasers and optics, along with a significantly lightened profile for faster transitions and handling. Finished in iconic Coyote FDE, this upper utilizes a short-stroke gas piston system, which keeps the action cleaner and cooler than traditional direct-impingement systems.
The conversion kit is a true “plug-and-play” solution, including the MCX Stock Adapter Kit to allow your AR-15 lower to interface with the MCX’s dual-recoil spring system—effectively eliminating the need for a buffer tube and allowing for a folding stock. It also comes with the SIG Duo Match Trigger Kit to ensure your lower’s fire control group is fully compatible with the MCX firing pin safety. The 9-inch barrel features a 1:5 twist rate, specifically engineered to stabilize heavy subsonic rounds and maximize accuracy with high-velocity supersonics. For the professional shooter or enthusiast demanding the most advanced 300BLK sub-carbine platform on the market, this conversion kit delivers the legendary performance of the SPEAR LT without the need for a whole new rifle.
Includes: Complete 9″ MCX-SPEAR LT Upper Assembly (FDE), MCX Stock Adapter (to allow mounting a folding stock to an AR-15 lower), Duo Match Trigger Kit, and User Manual.
Key Features
- Short-Stroke Gas Piston System: Virtually eliminates gas blowback into the action, increasing reliability—especially when running suppressed.
- SPEAR LT Lightweight Profile: Features a lightened barrel profile and slimmed-down handguard for superior balance and reduced overall weight.
- 300BLK Optimized 9″ Barrel: Cold-hammer forged steel with a 1:5 twist rate for exceptional stabilization of all .300 Blackout loads.
- Rigid Handguard: The redesigned SPEAR LT handguard uses improved mounting geometry to prevent rail flex, ensuring lasers and IR devices hold a repeatable zero.
- Bufferless Recoil System: Dual recoil springs are contained within the upper, allowing for the use of side-folding stocks and fire-while-folded capability.
- Complete Conversion Kit: Includes the necessary trigger and stock adapter to transform any standard Mil-Spec AR-15 lower into an MCX-SPEAR LT.
Product Specifications
- Brand: SIG Sauer
- Model: MCX-SPEAR LT Upper Conversion Kit
- Caliber: .300 Blackout
- Barrel Length: 9.0 Inches
- Twist Rate: 1:5
- Muzzle Threads: 5/8×24 TPI
- Finish: Coyote FDE (Anodized)
- Overall Length: 18.0 Inches
- Weight: 4.6 lbs
- MPN: UAMCX-300B-9B-LT-IR
- UPC: 798681726516
