BRN-4 Upper Receiver Assemblies
The Foundation of Your "Hell and Back" Rifle
The Brownells BRN-4® is an upper receiver assembly compatible with the Heckler & Koch HK416 parts. For many modern rifle enthusiasts, the HK416 is the ultimate evolution of the AR-15 platform, with a purpose-designed piston operating system that ensures outstanding reliability. Long coveted by AR-15 collectors, these guns have been scarce and prohibitively expensive in the U.S. Now, folks who want to experience 416 performance first-hand have a truly affordable alternative.
The HK416/BRN-4's piston and operating rod replace the AR-15's gas tube and eliminate one of the chronic problems of the older platform: hot gases and carbon fouling being blown back into the action. The BRN-4 runs cooler, cleaner, and smoother with a gentler recoil impulse. All of this makes for a pleasanter shooting experience.
BRN-4® parts are new-manufactured for Brownells: including the stripped receiver, bolt-carrier group, gas piston, operating rod, gas block (and pins), barrel nut, and handguard retaining screw. These parts will fit an original HK416, and if you have original HK416 internal parts or handguards on hand, they will fit the BRN-4®. It also uses an AR-15 charging handle, giving you a universe of aftermarket upgrade options.
The BRN-4® bolt-carrier group is compatible with the HK416 and MR556. It even has the cutout to accommodate tabbed MK556 barrels. The one-piece forged 8620 tool steel carrier has been extensively full-auto tested, so it's ready to take a pounding. And the 9310 tool steel bolt has an enlarged tail and increased surface area for fuller contact with the carrier to ensure smooth operation.
BRN-4® upper receivers come complete and fully assembled, minus a handguard and muzzle device. Any standard ½"-28 tpi threaded AR-15/M16 flash suppressor or compensator is fair game, and the BRN-4® will accept any handguard that fits the HK416 (we carry several). More good news: the BRN-4® upper fits on a standard AR-15 lower receiver.
You can get your BRN-4® with a variety of barrel choices. Manufactured for Brownells by Faxon, these 5.56 NATO chambered BRN-4® barrels (1-7" twist) are nearly identical to original HK416 barrels. We offer a Medium Contour, which is slimmer than the original to keep weight down and help you build a well-balanced rifle. We also offer a Heavy Contour that closely replicates the original HK416 barrel.
BRN-4® Upper Receiver Features
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Easy Learning Curve:
Classic AR-15/M16 forward assist and shell deflector, with a Magpul® Enhanced Ejection Port Cover. With the same user interface as the AR-15, a firearm with a BRN-4® is easy to transition to.
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AR-15 Compatibility:
The BRN-4® upper is compatible with standard, "mil-spec" AR-15/M16 lowers, giving you a huge array of options for completing your gun. Drop it on to a complete AR-15 lower, and you're good to go.
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Accessory Ready:
Handguard clamps onto the barrel nut with ONE crossbolt, with a tab on top of the receiver indexing into a notch on the handguard for precise alignment. A very strong, stable installation, yet very easy to remove for cleaning.
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Handguard Options:
Accepts handguards that fit the HK416 and MR556, including those by Midwest Industries (shown) and the Geissele Automatics Super Modular Rail HK handguard.
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Barrel Options:
Available with barrels in Medium or Heavy contour, with choice of durable Nitride finish or extra wear- and corrosion-resistant Chrome-Lined variations. All have standard 1/2"-28 tpi muzzle threads.
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Choose Your Barrel Length.
Building a pistol, SBR, or carbine? There's a BRN-4® with the right barrel for each, with the gas block tuned to deliver optimal reliability and recoil management for that length.
BRN-4® Upper Receiver Benefits
Ultra Dependable:
Proven short-stroke piston operating system is the same as that of the Heckler & Koch HK416, MR556, and G36. Built to go "to hell and back" and keep running like a top. Minimal additional weight over a standard AR-15.
Cooler Cleaner Easier To Shoot:
Minimal gas is needed to cycle the gun. Excess gas is vented forward from the gas block, AWAY from the shooter, for a more comfortable shooting experience. This also keeps heat and carbon fouling out of the action.
Simplicity Reliability:
Simple two-piece operating system replaces the AR-15's gas tube with a piston and an op rod. Fewer parts means fewer failure points and easier disassembly for cleaning. Minimal added weight over a standard AR-15.
Superb Accuracy Potential:
Longer barrel threads than an AR-15 allow for a longer barrel tenon, with a much larger barrel nut. The barrel is fully engaged to the upper and securely supported, leading to enhanced accuracy potential.
Monolithic Accessory Platform:
With its STANAG (M1913-type) top rail connecting continuously to an HK416 handguard, the BRN-4 provides a superbly stable structure for mounting optics and other accessories.
Rugged Gas System:
Forget about gas leaks or misalignment of the gas block. A tab on the gas block keys to a notch in the barrel, ensuring the block stays properly aligned, while two massive coil pins anchor it in place.
BRN-4® Upper Receiver Benefits
Introductory "Walkaround":
This is as close as we can get you to a "hands on" inspection of a complete BRN-4® upper assembly. Just add an HK416-compatible handguard and the 1/2"-28 tpi muzzle device of your choice.
Field Stripping Basic Maintaince:
We've talked about how easy it is to maintain a firearm with a BRN-4® upper. Brownells Gun Tech™ and video guru Caleb Savant shows us step-by-step how to do basic disassembly and cleaning of the BRN-4®.
Easy-To-Install Handguard:
Caleb walks us through installing a Midwest Industries HK416 handguard, but the BRN-4® upper will accept any handguard that fits an HK416 or MR556.
How To Swap The BRN-4 Barrel:
Caleb shows us how to do this surprisingly easy process. You can swap 13.7", 14.5" and 16" barrels. The 10.3" barrel uses a different gas block and piston assembly regulated for the shorter barrel length. Note: All NFA rules apply.
BRN-4® Upper Receiver Image Gallery
BRN-4® Model Comparison
Features:
SKU:
Barrel Length (in):
Length (in):
Weight (lbs):
Contour:
Gas Block (dia in):
Barrel Finish:
Bore:
BRN-4 16" Chrome Lined Assembled Upper
430106864
16
23.5
4.00
Medium
0.75
Phosphate
Chrome Lined
BRN-4 13.7" Chrome Lined Assembled Upper
430106863
13.7
21.7
3.7
Medium
0.75
Phosphate
Chrome Lined
BRN-4 10.4" Chrome Lined Assembled Upper
430106862
10.40
18.000
3.5
Medium
0.75
Phosphate
Chrome Lined
BRN-4® Upper Receiver Top Reviews
"Shot it suppressed and it runs like a top with minimal gas to the face!"- Franz B
verified purchaser
"Off the bat I was impressed with the attention to detail and the quality of the components.Everything about this upper is solid and feels duty grade."- Kevin S
verified purchaser
"Good quality, well designed for replicating a piston driven HK416."- John M
verified purchaser
BRN-4® Upper Receiver Product Cards
