The LMT Monolithic 5.56×45 NATO 10.5” Carbine-Length Barrel in Black (LMT part no. R-L7MA1B) is a factory-spec replacement barrel built for the LMT MRP monolithic upper receiver platform. At 10.5 inches with a carbine-length gas system, it’s a proven configuration for short-barreled 5.56 AR15 builds that still need reliable cycling with a full range of ammunition. The 1-in-7 twist rate stabilizes the heavier 5.56 NATO projectiles commonly used in military and duty loads. LMT manufactures these barrels to the same specification used on its contract carbines, so shooters get a drop-in match for existing MRP uppers.

Key Specifications

• Measures 10.5 inches long, a common short-barrel length for compact 5.56 AR15 carbines.
• Chambered in 5.56×45 NATO, the standard AR15 platform cartridge.
• Rifled with a 1-in-7 twist, stabilizing heavier NATO-spec 5.56 bullets.
• Finished in black for a durable, corrosion-resistant surface.
• Paired with a carbine-length gas system for reliable cycling at this barrel length.
• Compatible with LMT’s MRP monolithic upper receiver platform.
• Uses a standard barrel extension compatible with mil-spec 5.56 bolt carrier groups.

Frequently Asked Questions

Does this barrel fit any AR15 upper? It is built to mate with LMT’s MRP monolithic upper receiver system rather than a standard two-piece handguard setup.

Why a 1-in-7 twist rate? A 1-in-7 twist stabilizes a wider range of 5.56 bullet weights, including heavier projectiles used in military and duty ammunition.

Buy the LMT Monolithic 5.56 NATO 10.5-inch Carbine-Length Barrel, Black

Shop the LMT Defense monolithic barrel in our AR barrels selection, with fast, insured shipping from our Lubbock, Texas gun shop.