AR15 Upper Receiver Groups

AR15 Complete Upper Receiver Groups


Free Bolt Carrier Group with Purchase of Upper Receiver Group.  (Limited Time Offer)

BCM builds life-saving tools to meet the needs of professional soldiers, law enforcement, and responsible citizens. Each BCM complete upper receiver group is fully assembled, head-spaced, and test-fired prior to shipping.

Shop our AR15 complete uppers below. Click here to shop AR-15 upper parts for components including upper receivers, barrels, bolt carriers, muzzle devices, and more! 

More About BCM AR-15 Complete Upper Receiver Groups

Click the dropdowns below to learn more about every component used to assemble your complete upper receiver group.


BCM M4 Upper Receiver

BCM M4 upper receivers are machined to Mil-Specs from 7075 T6 forgings and equipped with our forward assist assembly and ejection port cover assembly, allowing the end user to upgrade or rebuild their individual components with other Mil-Spec parts in the future.

BCM MK2 Upper Receiver

The BCM MK2 Upper Receiver is built with up to 30% more rigidity than the current Mil-Spec M4 upper receiver without sacrificing interoperability for a mere additional 1/3 ounce of weight.

Upper receivers with integral carry handles and iron sights have been relegated to history. Optics are now synonymous with forward deployed carbines, featuring modular optics ready flat top upper receivers. Driven by a sense of urgency to improve effectiveness and save American lives in real-time, this innovation has inadvertently introduced a degradation in the rigidity of the upper receiver, with the weakest point being the area around the ejection port.

Shifting mass from non-critical to critical areas; the BCM MK2 Upper Receiver reduces barrel deflection and enhances bore tolerances improving barrel alignment, consistency, and accuracy.

This enhanced rigidity aids accuracy by limiting barrel deflection from external loads such as a bipod or vertical grip. This prevents unwanted deflection of moving components, reducing the chance for premature damage and wear of the bolt and barrel lugs which results from misalignment.

In addition to weapon optics, suppressors have also become standard in modern operations. With added gas expansion areas and new channels added around the charging handle opening, venting gas away from the end user's face reduces distractions when employing the weapon system with a can.

Fine-tuning the positioning of the forward assist creates additional clearance for right-hand-sided charging handle manipulation and clearance for end plate-mounted slings.

The MK2 Upper Receiver also retains all USGI components in the assembly and works with all USGI bolt carriers, charging handles, and barrel assemblies.

Machined from 7075T6 forgings, the BCM MK2 Upper Receivers retain a form following grain structure which maximizes achievable strength.

All of these improvements come without affecting the manual of arms employed in manipulating a Mil-Spec upper receiver.


BCM Barrel Materials

Every BCM chrome-lined barrel uses the same Independently Certified Mil-Spec 11595E Barrel Steel (CMV) used in the USGI M16 family of rifles. Built to perform in extreme environments, BCM barrels are stronger and more durable than typical commercial barrels due to high concentrations of carbon and/or vanadium in the alloy.

A chrome-lined bore and chamber are now a worldwide standard in the industry for an AR-15 rifle. The chrome bore and chamber is harder than the typical barrel steel and on the USGI M16/M4 rifles will aid in chambering, extraction, and reliability. It increases velocity and also resists fouling and corrosion from extended use in the field. This gives the end user a longer barrel life with less required time performing maintenance and cleaning.

Barrel Types

Standard (Button rifled)

Built to Mil-Spec using USGI NATO chambers and button rifling giving you a standard effective point and area target range that you would find on a military-issued rifle in the same configuration.

BFH™ (Cold Hammer Forged)

Originally pioneered by European armorers, hammer-forged barrels feature a honed interior finish and a tungsten carbide mandrel with the entire rifling pattern ground in relief onto its surface. The resulting barrel is both extremely durable and highly accurate. As with all BCM barrels, the BCM BFH series of barrels are made in the USA.

SS410™ (Stainless Steel)

Machined from 410 stainless steel with a 556 NATO Match Chamber. Featuring hand-lapped bore and chamber, 1/8 twist rate button rifling and M4 feed ramps barrel extensions, the 410 stainless barrel gives the shooter an excellent balance of weight and accuracy. 410 stainless is also harder and more corrosion resistant than conventional 416 stainless found in other precision barrels.

Barrel Lengths

Based on the end-user preference and mission BCM barrels are available in multiple lengths to accommodate desired configurations including 20”, 18”, 16”, 14.5”, 12.5”, 11.5”, 9”, & 7” barrels.

Barrel Gas System Lengths

Rifle (18” to 20” barrels)

Rifle length systems as designed and fielded by the US Military in the original AR10, M16, M16A1, M16A2, M16A3, M16A4, and MK12. Optimized for 18-20" long barrels, this gas system reduces recoil impulse and delivers a smoother operating and more controllable weapon system.

Mid (14.5” to 16” barrels)

Mid-length systems deliver the same compact size of a carbine, with less overpressure and recoil as opposed to the USGI M4 Carbine gas system. Giving the smoother running platform. The mid-length system can also allow for a longer handguard and by extension, a longer iron sight radius for improved accuracy when engaging with iron sights.

Carbine (11.5” to 16” barrels)

Carbine length gas systems, as designed and originally fielded by the US Military in the XM177 carbine. The carbine length system was designed to be as compact as possible while reliably cycling rounds. The carbine length gas system is still in use, powering M4, M4A1, and MK18 carbines issued to members of the US Military today.

Pistol (7” to 12.5” 300 Blackout Barrels)

Pistol-length gas systems were designed to be even more compact than the carbine-length gas system for optimal reliability in BCM’s short 300 Blackout barrels.


5.56 NATO

300 Blackout

Barrel Profiles

Government (Standard and Lightweight)

Government profile barrels have a .750 gas block diameter; lightweight barrels use a .625 diameter gas block. Lightweight profile barrels are similar to government profile up to the handguard cap and then slimmer from the gas block mounting area forward.

BCM Enhanced Profiles (Lightweight and Medium weight)

ELW (Enhanced Lightweight)

ELWF (Enhanced Lightweight Fluted)

EMWF (Enhanced Medium Weight Fluted)

BCM proprietary tapered profiles eliminate the handguard cap shoulder and feature a sleek, light, yet durable barrel, in both standard button rifled, and BFH cold hammer forged barrels. The tapered profile keeps the barrel heavy where most of the heat is generated, and lighter where it is less.

With barrel weight at the rear of the barrel, the front end of the carbine feels lighter and can be driven faster from target to target. The ELWF and EMWF barrels are fluted for a more rigid design and offer a bit of weight savings. BCM’s enhanced lightweight uses a .625 gas block diameter and medium-weight barrels use a .750 gas block diameter.


About BCM Rail Systems

Designed to the specification of end users, BCM Rail Systems are built free float, for improved accuracy, with aircraft grade aluminum alloys, that are lightweight but do not compromise rigidity. Mission flexible platforms, ideal for end-user customization in the placement of optics and accessories such as light mounts, vertical grips, hand stops, lasers, and bi-pods; BCM Rail Systems are available in three interface systems.

The entire BCM Rail System fleet uses our patented lock up** system where self-locking cross bolts apply force at the 12 o’clock position of the handguard equally distributing force around the surface area of the rail. This ensures continuous top-center alignment of the rail and mitigates forward/backward movement of the handguard when the weapon system is fired.

All BCM Rail Systems and accessories unite state-of-the-art manufacturing with lightweight and durable materials to ensure components that last a lifetime, performing far beyond performance requirements established nearly six decades ago. Like all BCM rifles and accessories, all BCM Rail Systems are made in the USA.

KMR - Keymod™ Compatible

The BCM KeyMod Rail (KMR-Alpha) delivers a robust, ultra-light modular handguard for the AR platform, second to none on the market today.

Manufactured from aircraft-grade aluminum alloy, the KMR-A gives end users an extensive range of customization options, with seven KeyMod lined mounting surfaces and one with MIL-STD-1913 at the 12 o’clock position.

The KMR-A features ergonomics tailored to end-user requirements, with its reduced profile maximized for positive control of the weapon system in the lightest possible package. The KMR uses our patented lock up** system where self-locking cross bolts apply force at the 12:00 position of the handguard equally distributing force around the surface area of the rail.

MCMR - M-LOK®* Compatible

The BCM M-LOK Compatible* Modular Rail (MCMR) delivers the same optimized ergonomic profile and lock up** developed for the KMR-Alpha rail system, but with an M-LOK compatible interface.

Manufactured from aircraft-grade aluminum alloy, the MCMR is both rigid and lightweight, featuring mounting interfaces on seven sides in addition to the MIL-STD-1913 at the 12 o’clock position.

QRF - 1913 Picatinny Rail Compatible

A MIL-STD-1913 rail, the BCM QRF (Quad Rail Free Float) Rail System is built with Picatinny Rails running the full length of the handguard at 12, 3, 6 and 9 O’clock. Precision machined from high-strength lightweight aerospace 6061-T6 Aluminum Alloy, the BCM QRF features the same lock up** as a steel barrel nut ensuring the rail resists movement even under extreme use.

Capable of mounting optics, laser and other accessories along the length of the system at 12, 3, 6 and 9 o'clock, the extended length railed handguard allows for faster manipulation and improved accuracy when engaging targets at close to intermediate ranges.

The system is also free floated, minimizing possible mechanical pressure distortions to barrel alignment and allowing barrel vibration to occur at its natural frequency for more accurate shots.

** Bravo Company MFG, Inc. US Patent 8904691

Drop-in Options

Models are available without a free float hand guard to allow the use of the installed Delta Ring, handguard retaining cap, and a separate drop-in handguard. BCM PKMR and BCM PMCR Polymer Handguards are available as an additional option for purchase on many models.

Variety of Handguard Lengths

BCM Handguard lengths available to accommodate different gas systems, barrel lengths, and personal preferences including:

KMR-A7, KMR-A8, KMR-A9, KMR-A10, KMR-A13, KMR-A15, & KMR-A17 for Keymod Compatibility.

MCMR-7, MCMR-8, MCMR-9, MCMR-10, MCMR-13, & MCMR-15 for M-LOK* Compatibility.

QRF-7, QRF-8, QRF-9, QRF-10, & QRF-12 for 1913 Picatinny Quad Rail Compatibility.

*M-LOK® is a registered trademark of Magpul Industries Corp. -


Muzzle Devices

Every AR-15 complete upper receiver group comes standard with an A2 Flash hider. Optional flash hiders, compensators, muzzle breaks, and suppressor-ready muzzle devices can be installed from the pick lists before purchase.

BCM offers a variety of muzzle devices from the original USGI A2 comp to BCM’s full line of compensators. All factory installed.

Compensator types

BCM Compensator Mod 0, Mod 2, Mod 4, and Mod 6 are shorter. Similar in length to an A2 flash hider.

BCM Compensator Mod 0 is designed primarily for recoil mitigation.

Compensator Mod 2, Mod 4, and Mod 6 are designed primarily for flash reduction with muzzle rise compensation. These mods all work similarly with their primary difference being the aesthetics.

BCM 14.5” barrel complete upper receiver groups only:

BCM Compensator Mod 1, Mod 3, Mod 5, and Mod 7 are longer in-length and predrilled to permanently mount (per BATF specs) to a 14.5” barrel to bring length out over 16” +.

BCM Compensator Mod 1 is designed primarily for recoil mitigation.

Compensator Mod 3, Mod 5, and Mod 7 are designed primarily for flash reduction with muzzle rise compensation. These mods all work similarly with their primary difference being the aesthetics.

Charging Handles

Enhanced charging handle options are available in single-sided and ambidextrous models.

Bolt Carrier Group

Bolt Carrier Groups can be added to your complete upper receiver purchase. These are the same BCM bolt carrier groups that feature the industry gold standard in quality.

The BCM Bolt Carrier Group features a parkerized exterior and chrome lined inside carrier, machined to support automatic fire and properly hardened parts to ensure a strong staking and proper gas system functioning.

Works in any Mil-Spec AR15, M16, or M4.

The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength. Also includes a tool steel machined extractor and ejector, BCM Extractor Spring, and HPT (High-Pressure Tested), and MPI (Magnetic Particle Inspected).

Machined to USGI specifications, this M16/M4 carrier includes the proper Mil-Spec gas key. The gas key is chrome lined and heat treated, per GI specifications, secured to the carrier via USGI domestic manufacturing Grade 8 fasteners, and properly staked per Military Specifications.


BCM Product Testing & QC

Quality control is paramount at BCM. For decades BCM has set the industry standard for dimensional and mechanical quality control with a focus on reliability. BCM has designed in-house quality control inspection processes that far exceed the industry mil-standards and has been implemented into many of the USGI supply lines.

Every BCM product is designed, engineered, tested, and quality control inspected in-house. In making life-saving tools, we want to ensure every component is in spec, functioning properly, and is reliable.

Assembled Complete Upper Receiver

Prior to shipping all BCM complete upper receiver groups are test fired for function. Models with forged front sight bases are laser bore sighted with a Mil-Spec carry handle for sight alignment within Mil-Specs. Then batch samples are test fired for accuracy. PLEASE NOTE: Each upper receiver group will show handling marks consistent with our in-house quality control procedures.

As a note: BCM barrel components are parkerized separately before assembly.

Bolt Carrier Group

The available BCM Bolt Carrier Group goes through similar testing. Watch this video with Larry Vickers on our manufacturing and quality control process.


Bravo Company USA was founded in 2003 in the garage of a U.S. Marine veteran in Hartland, WI. Our mission was to support private security professionals in need of reliable Mil-Spec quality components for their weapons that were not easily accessible. Since then we have expanded our selection of innovative life-saving equipment, and have helped soldiers, law enforcement, and responsible citizens all over the globe.