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Sig Sauer MCX
California Proposition 65 Warning

This product can expose you to chemicals including lead, known to cause cancer and birth defects. For more info visit P65Warnings.ca.gov.

Sig Sauer

MCX

$1,699.99
Available California compliant

Sig Sauer MCX-Spear LT, Complete Upper Receiver, 300 Blackout, 9" Threaded Barrel, 5/8X24 Thread Pitch, Fits AR-15 Lower Receivers, Anodized Finish, Black, Includes Charging Handle and Bolt Carrier Group, 3-Prong/SIG Suppressor QD Muzzle Device UAMCX-300B-9B-LT-BLK

Key Details
Brand Sig Sauer
Manufacturer Part Number UAMCX-300B-9B-LT-BLK
UPC 798681682522
SKU SGUAMCX-300B-9B-LT-BLK
Current Stock 36 available
Quantity Updated May 7, 2026 12:50 PM
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Purchase Requirements
  • Final availability is confirmed at checkout.
In-Store Pickup Required: All firearm purchases must be picked up at our Beverly Hills location after background check completion.
Product Description

The MCX-SPEAR LT developed for the SF community is the most advanced platform of its kind. Convert any M4/AR15 platform into a modernized folding firearm with superior reliability, durability, and accuracy. This item includes a complete 9" 300BLK upper assembly. It features a removeable 3-prong flash-hider ready to accept a SIG SLH/SLX suppressor. Receiver extension delete stock adapter so you may mount any folding or static stock or brace that uses a vertical 1913 rail system.

Features
  • Adapts with Any M4/AR15 Spec Lower Assembly
  • Dual Rod Recoil Assembly Eliminates Buffer System
  • Adjustable Gas System
  • Quick Change Barrel Design
  • Ambidextrous Charging Handle with Gas Deflector
  • Tapered Bolt Design
  • Compatible with SLX/SLH Suppressors
  • M4 Adapter Allows for Picatinny Rail Folding Stock Capabilities
Specifications
UPC: 798681682522
Manufacturer: Sig Sauer
Manufacturer Part #: UAMCX-300B-9B-LT-BLK
Model: MCX
Model (Alt): Spear LT
Barrel Length: 9"
Capacity: N/A
Finish: Anodized
Sights: Flat Top
Type: Upper