AR-15 11.5″ 5.56/.223 BRT barrelled Upper Receiver

$499.00 $399.00

Out of stock



**Picture is not of actual item; actual upper does not have barrel nut unless purchased with installed handguard (optional add-on)**


This kit is the basic piece of a complete AR-15 upper receiver: an Aero Precision upper receiver (complete with ejection port cover and forward assist installed) and a 11.5″ Black River Tactical OPTIMUM CQB light 5.56 barrel with pinned low-profile gas block and carbine gas tube included.

Do you want a COMPLETE upper with handguard, muzzle device, BCG, and charging handle, all installed and ready to pin onto your complete lower?  Then just add on the parts you wish to have installed to your cart and we will install them to your upper.  *If you wish to assemble the parts yourself, please mention this in your order comments and we will ship the kit to you unassembled*


Barrel specs:

BRT 11.5″ OPTIMUM CQB Barrel

This length is ideal for close quarters, while still producing good velocities and terminal performance from 5.56 ammo.

BRT Gas Drive

The BRT Gas Drive provides exceptional smoothness with extreme reliability. The gas port size controls how much pressure is delivered to the action and therefore how much gas drive is available to cycle the action. Proper balance is critical to the reliability and longevity of the system.

BRT barrels are designed for reliable use with and without a suppressor attached. The results are an balance of wide reliability margin, smooth operation and seamless suppressor compatibility with near zero “gas to face” issues.

  • Buffer Recommendations
    • Unsuppressed: H or CAR, VLTOR A5H0
    • Suppressed: H2, VLTOR A5H2


The BRT OPTIMUM Close Quarters Battle Light profile combines art and science to maximize performance. While its smooth transitions and gentle tapers are organically inspired, the end result is backed by extensive analysis, design and testing. The profile is thicker near the chamber for better heat resistance and uniform thermal performance, tapering toward the muzzle to reduce weight and improve balance. The handguard cap shoulder is contoured to the .750″ diameter gas block journal, which is dimpled for simple installation of a BRT MicroPin gas block. The end result is a midweight, fast handling barrel with improved consistency across various loads and firing schedules.

CAR Length Gas System

The Carbine length gas system provides OPTIMUM performance from 11.5″ barrels. The gas system length controls the timing of the gas cycle and overall gas drive available. The Carbine length gas system allows exceptionally smooth cycling with maximum reliability under extreme conditions.

Suppressor Ready 1/2″-28 Muzzle Thread

Precision cut threads are specified to a tighter tolerance and better bore alignment than standard threads, while maintaining compatibility with all common muzzle devices.

Match Grade Blank

A great shooting barrel starts with a superior blank. Certified bar stock is deep hole drilled and precision reamed. The blanks are then CNC honed on state of the art equipment to produce a uniform bore diameter with less than .0002″ variation from chamber to crown. This level of uniformity and roundness exceeds what is generally possible even with hand lapping.

6P Rifling 1/7 Twist

6P rifling improves upon conventional rifling in several important ways. The hybrid poly groove design produces less bullet deformation allows better exterior ballistics. In addition, the sides of the lands are sloped and blended to reduce fouling and further reduce bullet jacket stress. The optimized land-groove ratio minimizes engraving forces while boosting projectile velocity.

The 1/7 twist rate stabilizes the heaviest projectiles in extreme environments, while producing excellent performance from lighter training and varmint projectiles.

4150 CrMoV Barrel Steel

This is the same grade of steel specified by the US military for nearly all small arms barrels due to its excellent heat resistance and uniform grain structure. The addition of Vanadium and increased Carbon sets this alloy apart from the steels commonly used to make barrels offered in the commercial market. This steel is inspected and certified to meet strict requirements of chemistry and composition at the mill before continuing on to be made into a barrel blank.

Melonite QPQ

BRT barrels are treated inside and outside with the corrosion and wear resistant QPQ process. More than a surface finish, this treatment converts the outer surfaces of the steel into a hard composition with similar properties to hard chrome plating, but without any dimensional changes. This new surface improves extraction and velocity while resisting fouling and corrosion.

5.56 NATO chamber

This allows maximum compatibility wits all commonly available ammunition types, including military 5.56, brass cased .223 and steel cased .223. A properly dimensioned 5.56 NATO chamber offers maximum reliability and ammunition compatibility, while giving up almost nothing compared to SAAMI .223 Remington or .223 Wylde chambers.

M4 Barrel Extension

This includes enlarged and lengthened feed ramps to ensure smooth feeding of all ammunition types. The barrel extensions are finished separately from the barrels during their QPQ process to ensure critical parameters are unaffected. They are joined during final assembly, ensuring excellent longevity and performance.


    • BRT OPTIMUM CQB Light Profile (.750 Gas Block)
    • Carbine Length Gas System
    • BRT Gas Drive
    • 1/2-28 Suppressor Ready Muzzle Thread
    • 6P Rifling 1/7 Twist
    • 4150 CrMoV Steel per Mil-B-11595E(AR)
    • QPQ Nitride Chamber and Bore
    • 5.56 NATO Chamber
    • M4 Barrel Extension
    • Weight: 20.3 oz

Additional information


"Black River Tactical 16-inch 5.56 BRT OPTIMUM MPR"
"Stag Arms 16-inch SS fluted 5.56"


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