From The Vault: The Ultimate HK-416 Clone, The BRN-4

Introduction

Hey everyone, Caleb here from Brownells. In this From the Vault episode, I’m walking through my personal BRN-4 build—a project that originally started as a competition rifle for Gunfighter Gauntlet but ended up becoming one of my favorite rifles to shoot and tweak. If you're into HK416 clones or just want to see how I built mine out from the inside out, here's the full breakdown of parts, purpose, and performance.

BRN-4 Platform Overview

The core of this rifle is a Brownells BRN-4 upper and lower—our in-house take on an HK416-style setup. The lower is built to match the 416 footprint, and the upper comes with the 416-style short-stroke gas system and forged construction. I chose this platform because it gives you the ergonomics and reliability of the 416, while still staying modular with AR-15 parts.

Stock and MKII RMS Buffer System

At the rear, I’ve got a B5 Systems SOPMOD stock paired with a Bravo Company MKII RMS buffer system. It uses a VLTOR A5-length receiver extension but has BCM’s tuning behind it. The result? It’s super smooth under recoil and balances the rifle perfectly.

The end plate is from Forward Controls Design, and I’m also running their castle nut. Their stuff is built tough and looks clean without being flashy.

Geissele Trigger and Controls

Inside the lower, I’ve got a Geissele SD-C trigger, which I’ve used across a bunch of rifles. It’s predictable, crisp, and just gives me consistent hits. I paired that with a Radian Talon safety in a short-throw setup—just my preference for quicker transitions without over-rotating.

Optic and Mount

I’m running a Nightforce NX8 1-8x LPVO, mounted in a Geissele Super Precision mount. The mount gives solid return-to-zero and the scope itself has excellent clarity. It’s been banged around in matches and holds zero like a champ.

Upper Components and Handguard

The BRN-4 upper is fitted with a 10.4" HK416 profile barrel, which we source from Germany. I installed a Geissele MK15 handguard, which interfaces perfectly with the 416-style upper and offers rock-solid lockup for accessories.

I also added a Geissele Super Charging Handle, which is one of the most comfortable and easy-to-grab CHs out there.

Muzzle Device and Suppressor

On the end of the barrel, I’ve got a Dead Air flash hider, which interfaces with my Dead Air Sierra 5 suppressor. It’s compact, full-auto rated, and performs great on this setup. The Sierra 5 is easy to mount and doesn’t throw off the rifle’s balance.

Lights, Lasers, and Controls

Mounted up front, I’ve got a Steiner DBAL-A3 for IR and visible aiming, paired with a SureFire weapon light. To control everything, I use a Unity Tactical Axon switch, which gives me a clean setup with tactile response—super helpful in low-light environments.

Forward Controls Parts

I’ve swapped out some of the lower parts with components from Forward Controls Design, including the bolt catch, mag release, and castle nut. These small upgrades make a big difference in feel and reliability without altering the rifle’s overall look.

Furniture and Accessories

The grip is a Magpul K2, which gives me the right wrist angle, and I’ve added a Multitasker Nano under the front rail using a MagPod on the PMAG. The Nano stays handy for zeroing or quick adjustments and the MagPod adds a bit of stability when I’m shooting from cover or prone.

Internals and BCG

Internally, the rifle runs a proprietary HK-style BCG and gas piston system. I’ve kept the factory piston setup because it’s reliable and built to last, especially when suppressed. Everything cycles clean, and I haven’t had a single issue under pressure.

Final Thoughts

This BRN-4 started off as a one-off match gun for Gunfighter Gauntlet, but it’s turned into a go-to rifle for me. The balance, reliability, and overall feel are exactly what I want from a 416-style build.

If you're looking to build something similar, this setup offers a great mix of precision parts, proven accessories, and thoughtful upgrades without going completely overboard.

Thanks for checking it out—if you’ve got questions about any of the components or want to see other builds, let us know in the comments or shoot us a message!

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