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Sig Sauer® MCX® SPEAR LT 11.5" 5.56 NATO Factory Replacement Barrel & Gas Block Assembly – Cold Hammer Forged – 1/2x28 Thread Pitch – Adjustable Piston Valve System – Matte Black – 8901313
Product Description
The Sig Sauer® MCX® SPEAR LT 11.5" 5.56 NATO Factory Replacement Barrel & Gas Block Assembly (8901313) represents the pinnacle of modern, multi-caliber mission adaptability, short-stroke piston logistics, and modular carbine staging engineering, natively forged in the USA to enhance or convert your tier-one weapons system. Purpose-built to serve as the definitive high-efficiency solution for close-quarters battle (CQB) profiles, vehicle operations, and low-profile tactical deployments, this assembly allows operators to instantly scale down their platform's overall longitudinal footprint without sacrificing mechanical reliability. While traditional direct-impingement short barrels frequently suffer from over-gassing, rapid carbon fouling, and volatile bolt velocities, the MCX SPEAR LT barrel system uses a dedicated piston-driven engine to establish a cooler, cleaner, and completely optimized structural cycle loop.
The core structural foundation of this 2.46-pound barrel package is built from a **premium cold hammer-forged steel blank**, precision-contoured to reduce front-end weight while preserving high-yield accuracy under intensive multi-magazine thermal strings. The chamber is tailored to standard 5.56x45mm NATO dimensions, ensuring seamless stabilization and velocity uniformity with heavy duty or match-grade defensive projectiles. The muzzle is completed with standard 1/2x28 TPI threads and includes Sig's signature tapered shoulder profile, guaranteeing perfect concentric alignment with specialized suppressors, muzzle brakes, and flash hiders. The entire exterior face is shielded with a hard-wearing, non-reflective matte black finish that isolates the core metal from harsh moisture exposure, carbon gas wear, and abrasive trail debris.
The true operational triumph of this factory-original conversion kit lies in its pre-installed, **two-position adjustable short-stroke piston gas block assembly**. Featuring a user-serviceable gas valve, this integrated layout allows the operator to quickly switch gas flow vectors to accommodate standard unsuppressed field training or high-back-pressure suppressed staging arrays. This prevents physical frame wear, minimizes bolt carrier bounce, and tames cyclic recoil into a smooth, completely predictable impulse. Engineered as a true drop-in component for the second-generation MCX platform, this 11.5-inch barrel conversion (798681675234) delivers an indispensable primary asset to maintain complete mechanical and tactical authority over your firearm architecture.
Includes: (1) Authentic Sig Sauer MCX SPEAR LT 11.5" 5.56 NATO Cold Hammer Forged Barrel, (1) Pre-Installed Complete 2-Position Adjustable Short-Stroke Gas Block & Piston Valve Assembly, Barrel Extension Coupling, Muzzle Taper Cap, Packed in Factory Original Protective Storage Sleeve Box.
*Administrative NFA Regulatory Guidance & Assembly Safety: The Sig Sauer 8901313 barrel assembly features an 11.5-inch short barrel footprint. WARNING: All National Firearms Act (NFA) rules and state regulations apply. Installation of this barrel onto an existing rifle lower receiver with a shoulder stock attached transforms the weapon into a Short-Barreled Rifle (SBR), requiring an approved BATFE Form 1 tax stamp prior to assembly. Alternatively, this component may be legally affixed to dedicated pistol lower receiver structures or existing registered NFA SBR configurations. Always visually and physically verify that your firearm is completely unloaded, cleared, and safe on your workbench before attempting any barrel swap routines.
Key Features
- Genuine Sig Sauer Factory Component: Engineered to exact original equipment manufacturer (OEM) tolerances for drop-in multi-caliber conversions on the MCX SPEAR LT.
- Short-Stroke Piston Gas Block: Includes a built-in, pre-aligned adjustable gas valve to seamlessly balance bolt speeds between unsuppressed operations and suppressed missions.
- Cold Hammer-Forged Longevity: Premium barrel profile delivers exceptional heat dissipation, repeatable long-term accuracy, and robust throat life across thousands of duty strings.
- Optimized 11.5" SBR Footprint: Provides the perfect balance of compact maneuverability and terminal bullet velocity, making it an elite option for vehicle transit or home defense.
- 1/2x28 TPI Tapered Muzzle: Integrated SIG taper shoulder ensures zero-play lockup and concentric tracking with modern muzzle devices and direct-thread suppressors.
- Complete Modular System: Ships with the full gas system pre-assembled on the barrel, removing the need for precision alignment drills or separate gas component staging.
Product Specifications
- Brand: Sig Sauer® Electro-Optics & Firearm Components (Crafted natively in the USA)
- Product Line: MCX® Modular Mission Adaptability & Caliber Conversion Logistics
- Model Designation: MCX SPEAR LT 11.5" 5.56 NATO Barrel and Gas Block Assembly
- SKU / MPN: 8901313 (Alternative Industry Identifiers: 8901313-Sig / SIG-8901313)
- Barrel Overall Length: 11.5 Inches (292.1 mm) Compact Tactical Deck
- Caliber System Optimization: 5.56x45mm NATO / .223 Remington
- Barrel Core Material: Cold Hammer-Forged Premium Structural Barrel Steel
- Muzzle Thread Standard: 1/2"x28 TPI (Threads Per Inch) with Tapered Shoulder
- Gas Operating System: Short-Stroke Gas Piston System
- Gas Regulator Profiles: 2-Position User-Adjustable Mechanical Valve
- Loaded Chamber Indicator: No (Clean Low-Profile Target Breach Face)
- Exterior Protection Finish: Scratch-Resistant Corrosion-Defeating Matte Black Finish
- Platform Host Compatibility: Sig Sauer MCX SPEAR LT Receiver Assemblies Exclusively
- Product Net Component Weight: ~2.46 lbs (~39.3 oz) - Lightweight Front-End Profile
- Total Packaging Shipping Mass: ~3.10 lbs (Enclosed Inside Protective Padded Shipping Staging Layer)
- UPC Barcode Number: 798681675234
