The LMT Defense 10.5-inch .300 Blackout barrel is a chrome-lined, 1:7 twist barrel made for LMT’s monolithic receiver and the MRP-L platform (LMT part no. R-L7BH1B). It arrives with a low profile gas block, a pistol length straight gas tube and an A2 birdcage, so it is built around a complete direct-impingement gas system rather than a bare tube. The barrel is coated and cryogenically treated for long-term durability, which suits a short .300 BLK upper that sees regular range use. For builders who want a compact, handy .300 Blackout upper on LMT’s own receiver, the 10.5-inch length is the configuration to start from.

Key Specifications

• Barrel length is 10.5 inches (266 mm), a compact length that keeps a .300 Blackout upper short and quick to handle.
• Chambering is .300 BLK, the cartridge this barrel is built around.
• Rifling twist is 1:7 right-hand, the rate LMT specifies for this barrel.
• Barrel material is chromoly (CB) with a chrome-lined bore, a combination chosen for wear resistance and easier cleaning.
• The barrel is coated and cryogenically treated for long-term durability.
• Operating method is direct impingement, the conventional AR-15 gas system.
• A low profile gas block is included, keeping the muzzle end of the barrel slim.
• A pistol length straight gas tube is included to match the barrel length.
• An A2 birdcage is included at the muzzle to reduce flash.
• The barrel is designed for the LMT monolithic receiver (MRP-L, Light platform), so it pairs with LMT’s own upper rather than a generic one.

Frequently Asked Questions

Which upper does this barrel go on? It is designed for LMT’s monolithic receiver, and LMT lists it on the MRP-L (Light) platform.

What comes with the barrel? LMT includes a low profile gas block, a pistol length straight gas tube and an A2 birdcage with this barrel.

What twist rate and chambering does it have? It is chambered in .300 BLK with a 1:7 right-hand twist and a chrome-lined chromoly barrel.

Buy the LMT 10.5-Inch .300 Blackout Barrel for MRP-L Monolithic Upper

Most barrel swaps mean sourcing the gas block, gas tube and muzzle device separately, then hoping they all match. This LMT barrel arrives with those pieces specified for it, which removes that guesswork on a monolithic upper. See the rest of our AR barrels and order from our Lubbock, Texas gun shop for fast, insured shipping.