Sig MCX Barrel

**SIG MCX LT 9″ Caliber Exchange Kit – 5.56 NATO** $776.93

**SIG MCX-SPEAR LT 11.5-INCH 5.56 NATO BARREL AND GAS BLOCK ASSEMBLY (CALX KIT)** $776.93

**Sig Sauer MCX-SPEAR LT 5.56 16" Tactical Rifle (Barrel Only)** $776.93

**Sig MCX SPEAR LT 9″ Caliber Exchange Kit – 300BLK** $776.93

Sig MCX Barrel – 5.56 NATO & 300BLK Caliber Kits | Mounts Plus

Looking to upgrade your Sig MCX rifle with a new barrel or caliber conversion? Mounts Plus carries genuine Sig MCX barrels and caliber exchange kits designed for seamless compatibility with Virtus, SPEAR LT, and Patrol models. Whether you’re switching from 5.56 NATO to 300 Blackout or optimizing for SBR or carbine-length use, our OEM barrels offer match-grade accuracy, factory fitment, and rugged reliability.

These Sig MCX barrel kits include everything you need for a smooth caliber change or upper build — including the barrel, gas block, and in some cases, handguards or bolts depending on the model.

🛒 Top Sig MCX Barrels & Caliber Exchange Kits

Product Name	Caliber	Length	Price
Sig MCX LT 9” Caliber Exchange Kit – 5.56	5.56 NATO	9.0"	$776.93
Sig MCX LT 9” Caliber Exchange Kit – 300BLK	300 Blackout	9.0"	$776.93

⚙️ All MCX barrels are drop-in compatible with Gen 2 MCX upper receivers and include a barrel, gas block, and pre-aligned system for easy installation.

✅ Why Upgrade Your Sig MCX Barrel?

🎯 Caliber Flexibility – Swap between 5.56 and 300BLK with OEM precision
🔧 Drop-In Installation – Kits include necessary hardware for a hassle-free fit
🔄 Perfect for Suppressed or Compact Builds – Optimize your MCX for any use case
🛡️ Built for Duty – Factory-tested components for professional applications
🏆 Trusted by Professionals – Used by military and law enforcement around the world

📐 Barrel Lengths & Use Cases

🔹 9-Inch Barrel

Ideal for compact SBR and suppressed builds. Balances maneuverability with accuracy.

🔹 16-Inch (optional model)

Maximizes muzzle velocity and range. Perfect for full-length patrol rifles or range use.

Want other lengths or calibers? Contact our support for special-order MCX barrel kits.

🔍 Sig MCX Barrel Compatibility

✅ MCX Virtus
✅ MCX Patrol
✅ MCX SPEAR LT
✅ MCX Rattler (with proper gas system)
❌ Not compatible with MCX Gen 1 or Copperhead without modification

🛠️ Installation Overview

Uses standard MCX upper receiver interface
Gas block included and aligned
Swap barrels in minutes using basic gunsmith tools
Maintain original handguard or upgrade for modular fit

Need tools? Shop Gunsmithing Tools →

📚 Frequently Asked Questions (FAQ)

Q: Are these barrels factory Sig Sauer parts?
A: Yes. All kits listed here are OEM Sig Sauer caliber exchange kits and include matched components.

Q: Can I switch calibers with just the barrel?
A: Yes. Each caliber exchange kit is designed to convert your MCX to a new caliber, including barrel and gas system parts.

Q: Will this fit my MCX Rattler?
A: These kits are optimized for Virtus and SPEAR LT. Some parts may be compatible with Rattler if configured properly.

Q: Do I need to change the bolt or carrier?
A: For 5.56 and 300BLK, the bolt is typically compatible. Always verify with your original model specs.