Sig Sauer
MCX-SPEAR LT 6 AR CONVERSION KIT 300BLK - FDE
Item # SIG WUAMCXA-300B-6B-LT-FDE MSRP $1,999.99PRODUCT DETAILS
TECH SPECS:
Transform your MIL-SPEC AR-15/M4 lower into a top-performing SIG MCX-SPEAR LT platform with this complete factory conversion kit finished in Flat Dark Earth (FDE). Designed for shooters who want MCX performance without purchasing an entirely new rifle, this kit delivers the reliability, compact form factor, and suppressor compatibility that defines the SPEAR LT system.
This package includes a complete 6" 300 Blackout upper assembly equipped with a removable 3-prong flash hider that is ready to accept SIG’s SLH and SLX suppressor systems. Also included is the receiver extension delete stock adapter, allowing you to mount any folding or static stock/brace built for a vertical 1913 rail system—eliminating the buffer tube and opening the door to true MCX-style configuration.
Built to SIG’s exact engineering standards, the MCX-SPEAR LT upper is optimized for suppressed and short-barrel performance, making it ideal for compact defensive setups, vehicle storage, or modern PDW applications. The 300 BLK chambering excels in both subsonic and supersonic loads, providing outstanding performance across a variety of shooting environments.
This conversion kit is compatibility-focused, designed to work with MCX, M400, SIG 516, and any MIL-SPEC AR-15/M4 lowers, giving you MCX capability without platform replacement.
Key Features
-
Converts any MIL-SPEC AR-15/M4 lower to MCX-SPEAR LT configuration
-
Complete 6" 300 Blackout upper assembly in FDE
-
Includes receiver extension delete adapter for 1913 stock/brace systems
-
Removable 3-prong flash hider, suppressor-ready (SLH/SLX compatible)
-
Thread pitch: 5/8x24
-
Works with MCX, M400, SIG 516, AR-15/M4 MIL-SPEC lowers
-
Compact, high-performance SBR/PDW configuration
-
?? NFA Disclaimer / Legal Notice
This upper receiver has a barrel length under 16 inches. When installed on a rifle-configured lower, it constitutes an NFA-regulated Short Barrel Rifle (SBR) and requires registration and payment of a tax stamp through the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Additional state and local restrictions may apply.
It is the buyer’s sole responsibility to comply with all federal, state, and local laws.
| MCX-SPEAR LT Conversion Kit 6" 300 BLK FDE (WUAMCXA-300B-6B-LT-FDE) | |
|---|---|
| Upper Assembly | Complete 6" 300 BLK Upper |
| Caliber | 300 Blackout |
| Thread Pitch | 5/8x24 |
| Flash Hider | Removable 3-Prong – SLH/SLX Suppressor Ready |
| Color | Flat Dark Earth (FDE) |
| Stock Interface | 1913 Vertical Rail Adapter Included |
| Receiver Extension | Delete Adapter Included |
| Compatible Lowers | MCX, SIG M400, SIG 516, MIL-SPEC AR-15/M4 |
| Barrel Length | 6 inches |
| NFA Status | Short Barrel Upper – SBR Rules Apply When Assembled |
| Intended Use | Conversion Kit – Upper Receiver Assembly |
Questions 0
Ask a QuestionProven Arms & Outfitters A bolt-action rifle requires the shooter to manually operate a bolt to load a round, eject the spent casing, and chamber the next round. In contrast, a semi-automatic rifle is designed to automatically eject the spent casing and chamber a new round with each pull of the trigger. Semi-automatic rifles offer faster follow-up shots, while bolt-action rifles are typically more accurate due to their design.
SORT BY MOST RECENT
No Customer Review on this product
PRODUCT DETAILS
TECH SPECS:
Transform your MIL-SPEC AR-15/M4 lower into a top-performing SIG MCX-SPEAR LT platform with this complete factory conversion kit finished in Flat Dark Earth (FDE). Designed for shooters who want MCX performance without purchasing an entirely new rifle, this kit delivers the reliability, compact form factor, and suppressor compatibility that defines the SPEAR LT system.
This package includes a complete 6" 300 Blackout upper assembly equipped with a removable 3-prong flash hider that is ready to accept SIG’s SLH and SLX suppressor systems. Also included is the receiver extension delete stock adapter, allowing you to mount any folding or static stock/brace built for a vertical 1913 rail system—eliminating the buffer tube and opening the door to true MCX-style configuration.
Built to SIG’s exact engineering standards, the MCX-SPEAR LT upper is optimized for suppressed and short-barrel performance, making it ideal for compact defensive setups, vehicle storage, or modern PDW applications. The 300 BLK chambering excels in both subsonic and supersonic loads, providing outstanding performance across a variety of shooting environments.
This conversion kit is compatibility-focused, designed to work with MCX, M400, SIG 516, and any MIL-SPEC AR-15/M4 lowers, giving you MCX capability without platform replacement.
Key Features
-
Converts any MIL-SPEC AR-15/M4 lower to MCX-SPEAR LT configuration
-
Complete 6" 300 Blackout upper assembly in FDE
-
Includes receiver extension delete adapter for 1913 stock/brace systems
-
Removable 3-prong flash hider, suppressor-ready (SLH/SLX compatible)
-
Thread pitch: 5/8x24
-
Works with MCX, M400, SIG 516, AR-15/M4 MIL-SPEC lowers
-
Compact, high-performance SBR/PDW configuration
-
?? NFA Disclaimer / Legal Notice
This upper receiver has a barrel length under 16 inches. When installed on a rifle-configured lower, it constitutes an NFA-regulated Short Barrel Rifle (SBR) and requires registration and payment of a tax stamp through the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Additional state and local restrictions may apply.
It is the buyer’s sole responsibility to comply with all federal, state, and local laws.
| MCX-SPEAR LT Conversion Kit 6" 300 BLK FDE (WUAMCXA-300B-6B-LT-FDE) | |
|---|---|
| Upper Assembly | Complete 6" 300 BLK Upper |
| Caliber | 300 Blackout |
| Thread Pitch | 5/8x24 |
| Flash Hider | Removable 3-Prong – SLH/SLX Suppressor Ready |
| Color | Flat Dark Earth (FDE) |
| Stock Interface | 1913 Vertical Rail Adapter Included |
| Receiver Extension | Delete Adapter Included |
| Compatible Lowers | MCX, SIG M400, SIG 516, MIL-SPEC AR-15/M4 |
| Barrel Length | 6 inches |
| NFA Status | Short Barrel Upper – SBR Rules Apply When Assembled |
| Intended Use | Conversion Kit – Upper Receiver Assembly |
SORT BY MOST RECENT
No Customer Review on this product
Questions 0
Ask a QuestionProven Arms & Outfitters A bolt-action rifle requires the shooter to manually operate a bolt to load a round, eject the spent casing, and chamber the next round. In contrast, a semi-automatic rifle is designed to automatically eject the spent casing and chamber a new round with each pull of the trigger. Semi-automatic rifles offer faster follow-up shots, while bolt-action rifles are typically more accurate due to their design.
