Mrp-L M-Lok Specwar 5.56Mm 11.5'' Assembled Upper Receiver

The LMT Defense MRP-L M-Lok Specwar 5.56mm assembled upper receiver brings professional-grade engineering to your AR platform build. This upper pairs a monolithic receiver and handguard machined from a single piece of aerospace-grade aluminum with the rigidity and accessory flexibility modern shooters demand. Built in collaboration with specialized operators, the Specwar upper balances combat-proven design with practical features for everything from duty carbines to precision shooting platforms.

What sets this upper apart is its approach to mounting and ergonomics. The M-Lok pattern rail system gives you flexible accessory real estate without the bulk of older quad-rail designs, while a continuous Picatinny top rail ensures co-witness of optics and laser aiming devices—critical for night operations and low-light scenarios. The single QD sling attachment point is positioned aft for clean rigging without interference. The 11.5" configuration delivers a compact profile without sacrificing sight radius or barrel dwell time in 5.56mm.

The barrel seats via LMT's proprietary two-bolt locking system, accessible from the right side of the receiver and tightened with a standard T-30 Torx wrench. This design maintains the barrel-swap capability that keeps your upper flexible, while the monolithic architecture eliminates the flex inherent in traditional two-piece designs—essential when mounting illuminators or laser devices that demand rock-solid zero retention. The upper is assembled and ready to pair with your lower receiver and bolt carrier group.

Compatible exclusively with LMT monolithic barrel assemblies (which include a low-profile gas block and straight gas tube), this upper receiver represents a commitment to integrated system design rather than generic parts-bin assembly.

Key Features

• Monolithic receiver and handguard from single aerospace-grade aluminum forging
• M-Lok pattern rail mounting with full-length Picatinny top rail
• Proprietary two-bolt barrel locking system (T-30 Torx tool only)
• Aft QD sling attachment point for clean rig setup
• Optimized ergonomics and accessory real estate for mounted optics and night devices
• 11.5" length for compact platform with retained sight radius
• Barrel-swap capable design

Specifications

Frequently Asked Questions

What barrels are compatible with the Specwar MRP-L upper?

This upper receiver requires LMT monolithic barrel assemblies. It is designed to accept barrels of 12" or greater, and works with LMT's 12.5" MRP barrel system.

What lower receiver will this upper accept?

The product record does not specify lower receiver compatibility details. Contact Bosque Outdoors for guidance on pairing this upper with your lower.

Is this upper pre-assembled and ready to use?

Yes, the upper receiver arrives fully assembled. You'll need to source a compatible lower receiver, bolt carrier group, and charging handle to complete the rifle.

Can I mount night vision or laser devices on this upper?

Yes. The monolithic design and continuous Picatinny top rail provide a rigid platform specifically engineered for mounted optics, laser aiming devices, and illuminators. The M-Lok handguard also supports accessory mounting.

What tools do I need if I ever need to remove the barrel?

Only a standard T-30 Torx wrench is required to access and tighten the two barrel locking bolts.