Sig MCX SPEAR LT 9″ Caliber Exchange Kit – 300BLK
Not Yet Rated | Write the First Review SKU: 222-SIG-WCALX-MCX-300B-9B-LT
UPC: 799000000000
MFG#: WCALX-MCX-300B-9B-LT

Sig MCX SPEAR LT 9″ Caliber Exchange Kit – 300BLK

Suppressor-Ready Stealth Power. Compact. Modular. Mission-Driven.

Step into true modular performance with the Sig MCX SPEAR LT 9″ Caliber Exchange Kit in .300 Blackout (300BLK)—a factory Sig Sauer upgrade designed to transform your MCX platform into a suppressed-ready powerhouse. Whether you're fine-tuning your rifle for CQB, night ops, or home defense, this kit allows seamless conversion from your current caliber to .300 AAC Blackout, all in a compact 9" barrel configuration.

Built to the same demanding standards as the rest of the MCX SPEAR LT family, this Caliber X-Change Kit delivers unmatched flexibility, superior short-barrel performance, and full compatibility with modern accessories and suppressors.

🔧 Key Features:

• ✅ Factory Sig Sauer Cal-X Kit – Built to exact OEM specs for MCX SPEAR LT rifles and compatible upper receivers.

• 🎯 9” .300BLK Barrel – Perfectly balanced for short-barreled reliability, subsonic tuning, and suppressed operation.

• 🔇 Optimized for Suppressors – Barrel length and gas design make it ideal for suppressed or unsuppressed use.

• 🔁 Quick Swap Configuration – Installs easily, allowing caliber changes without permanent modifications.

• 💪 Compact & Tactical – Designed for SBR, pistol, or PDW-style configurations (NFA rules apply).

• ⚫ Matte Black Finish – Corrosion-resistant and non-reflective for duty or field conditions.

Compatibility:

• Designed for SIG MCX SPEAR LT systems

• Compatible with MCX upper receivers

• Ideal for builds where suppressor integration and short-barrel maneuverability are critical

⚠️ NFA Compliance Notice:

This 9" barrel assembly may only be installed on lower receivers that are:

1. Registered SBRs with the BATFE, or

2. Originally manufactured as pistols with no stock attached

⚖️ It is your responsibility to ensure all installations and use comply with federal, state, and local laws. Always adhere to NFA guidelines when working with short-barreled firearm components.

Technical Specifications: