Gun Review: Brownells BRN-180S Upper with BRN-180M Lower

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Two years ago Brownells launched the first of their Retro Rifles line, a series of ARs that are faithful copies of old school Eugene Stoner designs. While not technically part of the Retro Rifles collection due to some modern deviations from the originals, Brownells new BRN-180 upper and lower receivers pay homage to a unique rifle design with an interesting history.

BRN-180S BRN-180M Pistol

A very short note from the historical record:

Prior to its adoption by the U.S. military in 1964, ArmaLite sold the rights to the AR-15 design to Colt. Whoops. In an attempt to get a toehold back into that gravy train, ArmaLite decided to develop a competing rifle but had to do so without violating any of the AR-15’s patents. What they came up with was the short stroke gas piston-operated AR-18, eventually sold in semi-automatic flavor to the civilian market as the AR-180.

Unfortunately for ArmaLite, the AR-15/M16 ship had sailed and the AR-18 was too late to the party to receive any real consideration for military use. Likewise, though mostly for different reasons, the AR-180 never saw commercial success. At least, until now.

BRN-180S BRN-180M Pistol

Though it’s a too early to be sure, I think the time is right and the BRN-180 designs are right and I believe Brownells has a huge hit on its hands here.

The Upper:

The BRN-180 and BRN-180S uppers stand apart from AR-15 uppers in a few significant ways.

BRN-180S BRN-180M Pistol

Instead of a direct gas impingement system, the BRN-180 is driven by a short stroke gas piston. Ammunition combustion gas from the bore is bled off into a gas block in a similar fashion, but that gas then acts on a piston located right there at the gas block. This piston kicks rearward, impacting the bolt carrier and setting it in motion.

Excess gas is bled off at the gas block rather than traveling into the upper receiver and out through the ejection port via the carrier. No hot, dirty gases in the bolt carrier and inside the receiver lead to cleaner, cooler operation.

BRN-180S BRN-180M Pistol

Rather than a long bolt carrier that travels outside of the upper receiver and into a receiver extension (buffer tube), the BRN-180’s short bolt carrier and recoil spring system is contained entirely within the upper receiver itself. Two guide rods, firmly affixed at front and rear, hold the twin recoil springs in place and keep the carrier on track.

BRN-180S BRN-180M Pistol

Forgoing the oddly-located charging handle at the extreme rear of the upper, the BRN-180 features a fixed charging handle mounted to the bolt carrier. This handle reciprocates with the carrier, of course, and serves triple duty. Obviously it functions as a charging handle — pull rearwards to cycle the bolt to the rear — but it also acts as a forward assist and as a brass deflector.

All three of these decidedly not-AR-15-like features are faithful in function and, in particular in the case of the charging handle and dust cover, basic aesthetic design to that of the AR-18 on which the BRN-180 is based.

BRN-180S BRN-180M Pistol

Deviating from the original AR-18 design is a modern, free-float, aluminum handguard with M-LOK slots and top Picatinny rail.

With the guide rods removed from the upper (or, really, just pulled rearward about a half inch), a simple downwards pull on the locking collar at bottom rear of the handguard unlocks the handguard from the receiver and allows it to be pulled straight off the barrel. This very cool feature is a carry-over from the original AR-180 design.

BRN-180S BRN-180M Pistol

This review features a BRN-180S upper, which differs slightly from the BRN-180 uppers. The gas piston on the BRN-180S is easily adjusted between two settings: unsuppressed and suppressed, with a U or an S peeking through a hole in the handguard so you know where you stand.

A 90-degree turn on the front adjustment knob does the trick, allowing more or less gas through the block and ensuring that the extra backpressure from adding a suppressor doesn’t drive the piston too hard.

BRN-180S BRN-180M Pistol
BRN-180S gas piston components

On the rifle-length BRN-180 uppers (available in 16-inch and 18.5-inch), gas adjustment is a bit more involved. These uppers ship with two piston cups; unsuppressed and suppressed.

Swapping between modes involves removing the handguard, pulling back on the piston by hand to compress the spring, then lifting the cup up and out. Reverse the procedure to install the new cup. Simple, but certainly not as convenient as rotating a knob.

BRN-180S BRN-180M Pistol

Under the BRN-180S’ handguard is a 10.5-inch, 4150 steel barrel with a nitride finish. It’s chambered in .223 Wylde, which works great with both 5.56 NATO and .223 Remington, and has a 1:8 twist rate.

BRN-180S BRN-180M Pistol
Image courtesy Brownells

At the muzzle is a replica of the AR-180’s three-prong flash hider. This design, with its solid bottom half, provides muzzle rise compensation and prevents muzzle blast from kicking up dust. I’d assume the flash hider reduces muzzle flash to some degree, too.

Important note: the wrench flats behind the flash hider are not part of the flash hider, though it all looks quite integral. That’s a jam nut that allows easy timing of the flash hider (and a clean look) without the need for a crush washer.

To remove the flash hider, you’ll want to turn the jam nut clockwise as though you’re tightening it onto the gun while preventing the flash hider itself from rotating (or go ahead and turn it counterclockwise at the same time).

YHM Turbo K 5.56 Suppressor

Underneath the retro flash hider are standard 1/2×28 muzzle threads and a nice barrel shoulder. The BRN-180 and BRN-180S are ready for the addition of a silencer or other muzzle device. Seen above is a YHM Turbo-K, reviewed on the BRN-180S here.

BRN-180S BRN-180M Pistol

Wrapping up the many unique and cool features on the BRN-180 uppers is a rubber bumper on the left side. This nice little touch prevents your folding stock or arm brace from marring the upper’s finish. It can be removed if it isn’t to your liking.

brownells ar-180

Unlike the original AR-180, the BRN-180 upper receivers are compatible with standard AR-15 lower receivers. Though the BRN units don’t require a receiver extension, buffer weight, or recoil spring extending out of the lower, those parts won’t get in the way.

BRN-180S BRN-180M Pistol

Since a complete upper isn’t a firearm, you can order it from Brownells for delivery right to your door and slap it on a lower you already own. Just don’t forget the NFA stuff if you get a shorty upper.

The Lower:

BRN-180S BRN-180M Pistol

Like the upper, there are multiple BRN-180 lower receivers. The one featured in this review is the BRN-180M. I’m guessing the “M” stands for “modern,” as it’s a modern-styled, billet lower receiver. The other option is the BRN-180 lower, which is machined from a forging but maintains much of the look of the 1960’s, stamped steel original.

BRN-180S BRN-180M Pistol

Standard AR-15 parts fit the BRN-180 lowers. Except, of course, for the unnecessary receiver extension and its associated parts.

BRN-180S BRN-180M Pistol

Instead, gracing the rear of the lowers is an integral M1913 Picatinny rail. This allows for the use of folding stocks like the Black Collar Arms Stock Option or the SIG SAUER stocks, or folding pistol braces such as the SB Tactical FS1913, FS1913A, upcoming Triangle Brace, and others.

BRN-180S BRN-180M Pistol

Two modern, thoughtful touches I appreciated when assembling the BRN-180M stripped lower both revolved around set screws. One set screw (shoulder screw, more precisely) retains the bolt catch, hugely simplifying installation over trying to hold the bolt catch in place against its spring with one hand while holding a roll pin in place with another hand and hammering it in with your third hand.

Additionally, as there’s no end plate to retain the takedown pin’s spring and detent, those parts are inserted up through the bottom of the BRN-180 (in the area that’s covered by the pistol grip) and are held in place with a small set screw.

BRN-180S BRN-180M Pistol

Though I found it unnecessary, a polymer-tipped tensioning screw is there to remove any slack between upper and lower receivers ensuring a rattle- and wobble-free fit.

BRN-180S BRN-180M Pistol

I completed my BRN-180M lower receiver by installing an Elftmann Tactical ELF-SE trigger with straight trigger bow, an Elftmann Ambidextrous Speed Safety (or as I like to call it, the ELF ASS), an ODIN Works XMR 3 Extended Magazine Release, and an ERGO SWIFT Grip. All of the other parts kit-type parts were scavenged from an ERGO Grips Enhanced Lower Parts Kit.

BRN-180S BRN-180M Pistol

Machining, fit, and finish on the BRN-180M are absolutely fantastic. It’s a beautiful lower receiver in every way and it assembled flawlessly.

The Completed Product:

BRN-180S BRN-180M Pistol

If you like really nice AR-15s you’re going to like the BRN-180. A lot. It shoots and feels like a thoroughbred but in reality it’s a workhorse.

In the course of a few weeks we’ve put nearly a thousand rounds through the BRN-180S upper on the BRN-180M lower, and this thing’s a beast. Unsuppressed, suppressed, with the pistol brace folded to the side, with it or a shoulder stock extended (yes, a shoulder stock makes it an SBR with the short upper), out in the woods in near-freezing temperatures and out in oil country in the Texas heat and dust, it was always in its element.

This little guy from Brownells keeps on chugging and does so with a huge smile on its face. It absolutely loves sending rounds downrange and it’s one of the smoother, nicer-feeling short stroke piston guns I’ve shot. The BRN-180 is also compact and pretty darn lightweight.

BRN-180S BRN-180M Pistol

In fact, with the stock or brace folded the BRN-180S is extremely compact. A traditional AR-15 simply can’t compete with this.

BRN-180S BRN-180M Pistol

When suppressed, the BRN-180S beats any direct gas impingement AR-15 hands down. Not only did it seem quieter to me at the shooter’s ear than a standard AR thanks to the lack of high-pressure gas venting out through the ejection port, it sends no gas into the shooter’s face, either.

In part this, too, is because of the short-stroke piston system, but it’s also due to the lack of a rear-mounted charging handle. With the rear of the upper receiver sealed off, there are no gaps through which those eye-watering ammo combustion gases can jet into your face.


In short, the BRN-180 makes a fantastic suppressor host.

BRN-180S BRN-180M Pistol

While gas piston guns generally don’t enjoy a reputation for impressive accuracy, the Brownells BRN-180 . . . well it isn’t impressive. But it doesn’t disappoint, either. This 10.5-inch .223 Wylde is up for delivering 1 MOA to 3 MOA, 5-shot groups at 100 yards depending on ammo.

BRN-180S BRN-180M Pistol

Out on a west Texas hog hunt, this BRN-180S and BRN-180M combo dispatched a coyote at 40-ish yards and scared the heck out of a couple other coyotes at 650-ish yards. They were waiting for a cow to give birth so they could eat the calf, but a couple of 5.56 rounds whizzing by got them to turn tail. Even if the cow herself didn’t appear to notice the suppressed rounds, the coyotes sure did.

BRN-180S BRN-180M Pistol

Living in a racquetball racket bag, this setup, suppressed with a YHM Turbo K, has been by my side for weeks as my primary Coronazombie defense gun. After carrying it all around Texas and shooting it in varying weather suppressed, unsuppressed, and with all sorts of different ammo, I’ve come to trust the BRN-180. I’m happy with my choice of trigger and other components, and for Brownells’ part they’ve put together an absolutely awesome upper.

Compact, reliable, adjustable, accurate . . . I can’t think of a single darn thing I would change on the BRN-180S upper or the BRN-180M lower. Nor with the complete gun as built here. Though experimenting with different charging handle designs would be fun.

Specifications: Brownells BRN-180S Upper Receiver and BRN-180M Lower Receiver

Caliber: .223 Wylde (upper)
Capacity: 30+1 rounds (standard AR-15 magazines)
Operation: semi-automatic, short stroke gas piston operated
Barrel Length: 10.5 inches (BRN-180 available in 16-inch and 18.5-inch barrels)
Muzzle Threads: 1/2×28
Receiver Materials: 7075 aluminum receivers and handguard, Type III Hardcoat anodized
Overall Length: 19.5 inches (front of flash hider to face of rear Picatinny rail)
Weight: 5 pounds 11 ounces (fully built with flash hider, FS1913 brace, and all lower receiver parts pictured except magazine. No optic)
MSRP: $829.99 (upper…$719.99 at the moment) and $149.99 (lower)

Ratings (out of five stars):

Style and Appearance  * * * * *
I think both the upper and the lower look awesome. The right-side charging handle and lack of a receiver extension are unique and good looking, and the quality of the machining and anodizing are great.

Reliability  * * * * *
Rock solid.

Ergonomics  * * * * *
Many of us think there’s no improving on the ergos of an AR, but the BRN-180 proves that isn’t so. It keeps all the good parts, but gets rid of that awkwardly-placed rear charging handle and allows for the use of folding stocks and braces. Very cool.

Customize This  * * * * 
Ultimately, the BRN-180S is less customizable than a standard AR-15 upper since much of it is proprietary. This includes the barrel, which cannot be swapped by the end user.

Accuracy  * * * 
Probably fair to call this “average” for an AR-15.

Overall  * * * * *
Huge fan. Brownells nailed it on the BRN-180S, and pairing it with the BRN-180M makes perfect sense. As a complete gun, this thing is a rock star.


All images by Jeremy S. for TTAG unless otherwise indicated. 

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  1. Thanks for this article. I’ve always wondered a bit about what the AR-18/AR-180 were all about. Very detailed review.

  2. 1-3 MOA out of a 10 in. barrel isn’t impressive? Seems fine to me given how quickly the groups on 10 in. DI AR-15 uppers tend to open up as round count goes up. If you’ve got the time, you should do a follow-up with decent optics and match ammo and see what it can do.

    • That’s always how I do my accuracy groups. In this case I used a 5-30x SIG TANGO6 (a GREAT optic) and a few different brands of ammo including Federal Gold Medal Match, etc., plus affordable stuff like Armscor as always (which put up two like 1.8 MOA groups).

      • This gun hits so many things right I can forgive the slightly less accurate results. And it’s not 2000 dollars or more. I’d buy one right now but all the FFLs near me are either taking an hiatus or the stores are in weird lock downs. Since it’s a new offering it will be available in the fall when I usually make gun buys.

  3. Looks awesome. I’m not enthralled with reciprocating charging handles, but I can see the utility, since it can function as a ‘forward assist’. And the price seems quite reasonable.

    Now, if I didn’t already have more AR’s than I need….

  4. I think these AR180 uppers will become the thing as 3D printed guns continue to progress. You’ll be able to print a full lower subsystem stock and all after which you’ll pop your AR180 upper on and go.

    • It almost certainly would allow elimination of the weaknesses around the buffer tube area is my point.

  5. That’s very reasonable for the base gun, the ability to swing the stock in and make a pistol out of it takes the cake.
    I might be getting one after teotwawki ends and gun store return to normal.

  6. 300 Blackout is on the way. Spoke to Brownells, they say “soon” I’m waiting…

  7. IIRC Stoner designed the AR-18 to be manufactured by countries without the (at the time) sophisticated tooling needed to build the AR-15.
    Since it used metal stampings Armalite hoped to sell licensing rights.

  8. If the bolt carrier does not mechanically connect to the piston rod: it will hammer “contact surface” (anvil) it’s aligned with. It appears the piston rod just slaps the flat front of the bolt carrier. Commonly the bolt handle mechanical connects the piston rod to the bolt carrier, not so in this case. Sig 556s are mechanically connected, don’t need bolt carrier “return springs” and adjust at the gas port (Pos1 Normal gas, Pos 2 Adverse more gas) on long and short versions.

    “Different strokes” as they say. Lol

    • No sign of peening on contact surface between the piston and bolt carrier on any Vz. 58 I have seen, even after tens of thousands rounds. The piston must be in touch with the BC before it pushes on it as it cycles, it must not slap it.

  9. Simple way to install the bolt catch is to grab a metal coat hanger. Cut off the hook. Use the hook as a ‘slave pin’ to hold the bolt catch in line while tapping in the roll pin. The roll pin will push the slave pin out of the way. Done, no 3rd hand required. Work smarter, not harder.

    You also missed that the AR-18 was made under license in Japan by Howa and in the UK by Sterling who made a cute short rifle called the AR-180 SCS carbine. Had one back before the UK banned semi-auto full bore rifles and it was cool. You also missed the AR-18 is the foundation of nearly all short-stroke AR rifles; LWRCI, HK416 and others. It also influenced many other designs like the G36, the SAR-80 and the biggest rip off of the design, the SA80/L85.

    • Like it is with many billet lowers, the bolt catch pin hole isn’t open on the left side. A slave pin doesn’t work here. Great suggestion for other lowers, though, of course! But still not as nice as a shoulder screw, which also greatly lessens the opportunity to scratch your lower while trying to hammer in a roll pin. It’s also stronger than a roll pin (not that it really matters in this application, though, admittedly).

      On the missed stuff, perhaps you missed the “a very short note” comment that precluded my as-short-as-possible history section. This is a gun review of the new BRN-180, not a historical article on the AR-18 (which, if you’d like to write, we’d be happy to publish). Wikipedia alone has an extensive page on the history of the AR-18, which would have easily quadrupled the length of this review should I have included it. Actually, even you missed A LOT of interesting historical AR-18 details in your comment! In fact, I can’t believe you left out the fact that it was used in the Lebanese civil war. Quite the oversight, frankly.

  10. Can you remove the piston without removing the yhm muzzle brake ?
    Was wondering if enough clearance to do so ?

  11. Apologies for the noob question, but what would be the advantages and disadvantages of the BRN-180S chambered for .300 BLK (which has a 1/2-inch shorter barrel length at 10 inches). I’ve only ever owned a Ruger Mark IV .22 rimfire pistol and only shot 40 rounds through it to boot, but I want to improve my firearm knowledge and experience moving forward.

    • 300 Blackout fires a fatter, heavier bullet than .223/5.56 does, but at a slower speed because there’s effectively the same amount of gunpowder behind both (they use the same case and just have different bullet diameters). 300 BLK’s biggest advantage is when used in conjunction with a suppressor, as it was designed to fire subsonic bullets as well as supersonic. Subsonic is significantly quieter, supersonic maintains longer range capability. If you aren’t shooting suppressed, then there’s really no reason to shoot subsonic 300 BLK loads and it’s more of a toss up between the two calibers. I’d just as soon go .223 for the much cheaper ammo options. If I wanted to hunt deer and hogs I might lean toward 300 BLK for the larger, heavier projectile, if I wanted to hunt coyotes and such I’d lean toward .223.

      There are no BRN-180 specific advantages or disadvantages to going with either caliber. It’s strictly a caliber preference question or a question of which caliber fits your intended use better.

      • Thanks for taking the time to type such an informative answer, Jeremy. I was a newspaper writer for eight years and tutor writing at a community college right now, and I appreciate clear and concise writing–the earmarks of a good writer–and you’re good at that. I’m interested in the BRN-180S upper to start building my rifle based on the research I’ve done–your excellent, thorough review was part of that–but Brownells seems to be out of stock of everything. Either there’s been a run on firearms due to “protester/looter” fears, or COVID-19 has causes supply-chain disruptions, or both. Any suggestions for how I would go about finding one at a gun retailer near me? Or, do I just have to call around/check stores’ websites or retailers online? I wish I could find a firearms mentor near me to help me, but that doesn’t seem to be easy to do.

        • It’s both causes and there’s nothing in stock anywhere. Every major distributor is completely out of everything except for some target style .22 LR pistols. There are literally no semi-auto handguns or rifles in the supply chain. There’s no ammo. The best way to get a BRN-180 specifically is probably backordering it, if brownells allows that on this product, and waiting 🤷‍♂️. For finding something in stock the best bet is probably hitting up smaller, less popular dealers in your area or likely paying a premium on GunBroker.

  12. A former journalist question: I’m imagining you are loaned the components you review and have to return them? Just wondering.

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