Sig Sauer MCX-SPEAR LT 16" AR Conversion Kit – 5.56 NATO (UAMCX-556N-16B-LT-TT-R4XT)
Upgrade your existing AR-15 lower into a modern, lightweight, and suppressor-ready platform with the Sig Sauer MCX-SPEAR LT Conversion Kit. This complete upper assembly delivers the advanced short-stroke gas piston system, improved ergonomics, and reduced recoil of the MCX-SPEAR LT while retaining compatibility with your favorite mil-spec AR-15 lower receiver, trigger, and grip.
The kit includes a 16" hammer-forged 5.56 NATO barrel, folding/telescoping stock, M-LOK handguard with vertical grip, Romeo4XT-PRO red dot optic, and a removable 3-prong flash hider optimized for Sig Sauer SLH and SLX suppressors.
Key Specifications:
- Caliber: 5.56 NATO
- Barrel: 16" hammer-forged
- Gas System: Short-stroke piston (adjustable for suppressed or unsuppressed use)
- Stock: Folding/telescoping
- Optic: Romeo4XT-PRO red dot included
- Handguard: M-LOK compatible with vertical grip
- Muzzle Device: Removable 3-prong flash hider (suppressor-ready)
- Weight: Lightweight design for improved handling
Why Choose the MCX-SPEAR LT Conversion Kit?
- Short-stroke piston system runs cleaner and with less gas blowback than traditional direct impingement — ideal for suppressed shooting.
- Modular design lets you keep your preferred lower receiver, trigger, and grip while gaining MCX performance and reliability.
- Adjustable gas system and included flash hider make it suppressor-ready right out of the box.
- Comes complete with a quality red dot optic, vertical grip, and folding stock — minimal additional parts needed.
- Backed by Sig Sauer’s reputation for innovation and proven durability in military and law enforcement applications.
Perfect for shooters who want the best of both worlds: the familiarity of an AR-15 lower combined with the advanced features of the MCX-SPEAR LT platform.
SPECIFICATIONS
| SKU | UAMCX-556N-16B-LT-TT-R4XT |
|---|---|
| Model | SIG MCX-SPEAR LT |
| Barrel Extension | MCX |
| Barrel Length | 16 in [406.4 mm] |
| Barrel Rifling Type | Hammer Forged |
| Bolt Carrier Group Included | Yes |
| Caliber | 5.56 NATO |
| Charging Handle Included | Yes |
| Color | Black / Flat Dark Earth (FDE) |
| Forward Assist | Yes |
| Free Floated Handguard | Yes |
| Handguard Length (in.) | 13 |
| Handguard Material | Aluminum |
| Muzzle Device | Clutch-Lok Tapered QD Flash Hider |
| Muzzle Thread Pitch | 1/2-28 |
| Operating System | Short-Stroke-Piston |
| Receiver Finish | Anodized |
| Twist Rate | 1:7 |
