Mrp-L M-Lok 5.56/300 Blk 9.25'' Assembled Upper Receiver

The LMT Defense MRP-L M-Lok 5.56/300 Blk 9.25" assembled upper receiver brings precision engineering and modularity to your AR build. Built on LMT's patented Monolithic Rail Platform, this forged aluminum upper integrates the receiver and handguard as a single rigid unit—eliminating the flex and play you get with two-piece designs. It's engineered for shooters who demand accuracy and durability, whether you're running 5.56 NATO, .300 Blackout, or exploring other compatible calibers on a modern sporting rifle.

The MRP-L is the carbine-length platform, designed to accommodate barrels from 10.5" to 18", making it adaptable for everything from suppressed short-range work to mid-distance precision. Barrel installation is straightforward: two locking bolts (accessible from the right side) are torqued down with nothing more than a T-30 Torx bit, using LMT's proprietary locking system. The integrated low-profile gas block and straight gas tube come already fitted to any LMT monolithic barrel you pair with it. M-LOK attachment slots run across all eight sides of the handguard, giving you full flexibility to dial in lights, optic mounts, or other accessories exactly where you need them. Four QD sling attachment points let you set up the rifle for your preferred carry method.

This is a no-compromise upper for builders who understand that a monolithic design—receiver, rail, and gas block in perfect alignment from day one—delivers the rigidity and repeatability that translates to tighter groups downrange. The aerospace-grade aluminum forging ensures longevity through thousands of rounds. Note that the upper receiver is sold assembled but without a barrel; you'll need to source a compatible LMT monolithic barrel assembly separately.

Key Features

• LMT Monolithic Rail Platform design: receiver and handguard forged as one rigid unit for superior accuracy and zero shift
• Proprietary two-bolt locking system—simple T-30 Torx installation, no gunsmith required
• Carbine-length platform compatible with 10.5" to 18" barrels
• M-LOK slots on all eight sides for unlimited accessory mounting flexibility
• Integrated low-profile gas block and straight gas tube with LMT monolithic barrels
• Four QD sling attachment points for multiple carry options
• Aerospace-grade forged aluminum construction for durability and longevity

Specifications

Frequently Asked Questions

What barrels work with the MRP-L 9.25" upper?

The MRP-L is designed to accept LMT monolithic barrel assemblies in your choice of caliber. Barrel length can range from 10.5" to 18". You'll need to source the barrel separately; the receiver arrives without one.

Can I use this upper with a standard AR-15 barrel?

No. The MRP-L requires LMT's proprietary monolithic barrel assembly because of the unique locking system and integrated gas block design. This ensures perfect alignment and reliability.

Is this upper compatible with my AR lower receiver?

Yes, the MRP-L upper mates to any standard AR-15 lower receiver. The upper and lower share the standard pin interface.

What tools do I need to install a barrel on this upper?

You'll need a T-30 Torx bit to torque down the two locking bolts. No other tools or gunsmith work is required for barrel installation.