BRN-180 Gen 3: The Latest Evolution Of Stoner’s Other Carbine

Photos by Kenda Lenseigne

Originally created as a homage to Stoner’s other design, the BRN-180 has undergone not so much an evolution, but a caterpillar-to-butterfly transformation. Almost no parts on the Gen 3 version will interchange with previous iterations, but the family lineage is still obvious. 

When Stoner came up with the AR-18, it was to provide countries with less advanced manufacturing capabilities a means to access a modern assault rifle, by substituting a stamped and folded sheet metal receiver for the AR-15’s machined aluminum components. 

The hard-to-make bolt carrier with its linear piston was swapped for a tappet system, but he retained the successful multi-lug bolt, adding twin recoil springs located inside the upper receiver. This design change allowed for the addition of a folding stock, which was a major improvement to the AR-15 in a market which favored compact carbines for operating out of vehicles. 

While the AR-18 was not a commercial success, it nonetheless paved the way for just about every other assault rifle using a short stroke gas piston adopted by a major military in the following half century. So much for historical background; how does Brownells’ version stack up?

BROWNELLS BRN-180 GEN 3 SPECS

• Caliber: 300 BLK
• Capacity: 30 rounds
• Barrel Length: 9 inches
• Overall Length (As Shown): 32 inches
• Weight (As Shown): 7.7 pounds
• MSRP: $1,200

UNDER THE HOOD

Perhaps the biggest departure from Stoner’s vision, the upper receiver is milled from solid aluminum, while the handguard appears to be an extrusion. This is driven by modern manufacturing methods — the up-front cost of making a set of stamping dies to press the receiver from sheet metal is prohibitive, especially for a comparatively short production run, whereas you can be making chips on a CNC machine for the price of creating the code. 

While purists will no doubt decry the historical heresy, there’s no debating the quality of the machine work that went into this product, which keeps getting better with every generation. Compared to the Gen 2, this one’s streets ahead in terms of fit, feel and finish. 

We requested the 9-inch-barreled 300BLK option for T&E, but there are others, including a 13.9-inch 223 Wylde with a pinned and welded muzzle device to bring it up to 16 inches total, as well as a 16-inch-barreled upper in the same caliber. 

We paired the shorty Blackout with an SBR’d SIG MCX lower receiver, as this is probably the most widely distributed, non-buffer tube lower in circulation right now. Rattler owners who want to add a 5.56 upper to the safe can save 500 bucks by going this route, rather than adding an MCX-LT to their shopping cart, so it’s an attractive proposition.

With a means to light off cartridges secured, it was time to get down to business. Starting out front, the 9-inch-long, 1/6 twist barrel is terminated in an A2-style muzzle device, which can be removed to access 5/8-24 threads. So, we did. To these, we added a Dead Air Mojave 9 suppressor in its short configuration. While Dead Air markets the Mojave as a pistol can, it’s right at home on a 300BLK, and its 8-ounce weight is appreciated on a short carbine. 

Behind the can is the handguard, which has received a few refinements since the second-gen version. There are seven rows of M-LOK slots spaced out around its 7-inch length, with a full Pic rail at the 12 o’clock position. The area over the gas block, which vents propellant gases to the atmosphere, is blanked off, preventing the shooter’s wrist from being sand blasted, but still allowing access to the four-position regulator. 

The gas block itself is secured to the barrel by means of both a keyway machined into the barrel shoulder, and a substantial roll pin. 

300BLK is a tricky cartridge to accommodate, as there’s a huge span of gas pressure and volume between heavy subsonic loads and fast-moving supers — add the variation in backpressure caused by different suppressor designs, and you have a recipe for a lot of customer service calls. We tried several different super and sub loads, as well as two different cans, and the upper was able to handle all of them reliably. 

The Gen 3 handguard is secured to the upper by means of a single bolt at the 6-o’clock position. This bears on the barrel at the chamber area and pulls the rail tightly against a dogleg keyed area between the two, making for a very secure and rigid connection, which appears to be resistant to deflection under pressure. 

We didn’t get the opportunity to test zero retention with a laser aiming module but are confident it would bend less than an MCX, judging on how difficult it is to remove. We wound up having to beat it into submission with a soft-faced hammer for the first couple of times we stripped it. 

One of the biggest differences between generations of BRN-180s is the charging handle. The first two gens used the traditional bent wire charging handle, which was attached to the bolt carrier and whipped back and forth on the right side of the receiver. 

The new version employs a non-reciprocating charging handle on the left side, and the slot in which it rides is sealed by a synthetic gasket, much like the Swiss Stgw 90. Although the handle is bent downward, if you use an optic with a bulky mount, you can still wind up scraping your knuckles if it’s positioned forward on the rail. Fortunately, the EOTech 3-9×32’s mount is very compact and stays out of the way, but we’d like to see an even lower handle, preferably one that also folds when not in use. Hopefully, the aftermarket will address this. 

On the other side of the receiver at the rear of the ejection port sits an aluminum shell deflector, which is held in place by a roll pin and is absent in the first two BRN-180s. They employed a traditional hinged dust cover to reduce ingress of contaminants to the receiver, but the new version has ditched this in favor of a sliding dust cover permanently attached to the bolt carrier. The good news is that you’ll never need to remember to close the cover. The bad news is ours broke.

We have no idea whether this is a one-off failure caused by a freak manufacturing fault, or whether it’s a design flaw. We do know that it didn’t cause the gun to stop firing, and the broken piece was simply grabbed through the ejection port and yanked out once it was discovered. 

Inside the upper receiver, the bolt carrier group rides on a pair of AR-18-style guide rods, like gens 1 and 2. 

Brownells added a steel rail to the third gen, which is bolted through the left side and keyed to the receiver, which should increase both longevity and reliability. The guide rods are held at their rear by a block, which is captured by a sliding catch in the back of the receiver — previous models would launch their guide rod apparatus across the room once you popped takedown pins and shotgunned the action, but in this version, they’re retained until you decide to pull them out. 

ROUNDS DOWNRANGE

To make our cobbled-together carbine perform, we added a Samson folding stock to the Pic rail at the rear of the MCX receiver, along with the aforementioned EOTech Vudu optic (see Dave Merrill’s review elsewhere this issue) and Dead Air can for the majority of testing. A SilencerCo Omega 30 was also used as a higher backpressure example. To this assemblage was added a Tac Shield sling designed by a dude who is the epitome of “been there, done that,” and who I’m proud to have in my close circle of “move a body” friends. While it’s a bit narrow for use on an M240, for a lightweight build like this, it’s damn near perfect.

After a quick zero, we shot the BRN-180 for groups, and from bags at 100 yards, it turned in 1.75 MOA with SIG 124-grain FMJ ammo, which was used for the first few mags to break in the action. Switching to Hornady SubX 190-grain rounds, the upper proved to be consistent; 1.25 MOA was easily achievable, though naturally, POI was about 8-MOA low from the supersonic zero. 

We ran the gun with its gas regulator set on position 2 for supersonic ammo and the low backpressure can, with position 4 needed to reliably run subs. The higher backpressure SiCo suppressor was run on position 1 and 3, respectively. 

Throughout all of our testing, the lack of gas to the face was remarkable, despite our initial misgivings about the effectiveness of the polymer seal around the charging handle slot. 

Compared to a similarly equipped AR-15, the difference was night and day, and not having to mess with buffer weights or springs was a bonus — just figure out what gas setting was needed for the combination of ammunition and suppressor, then flick the regulator over to that position. Due to the bolt carrier’s comparatively low reciprocating mass, recoil was very mild. 

With a can, the impulse of 124-grain rounds was about what you’d expect from an unsuppressed 5.56. 

What would we like to see changed? While the upper is very good, there’s a couple of things we think can be improved upon from a user perspective. The first is the method of handguard removal, which is necessary to access the gas system for normal cleaning and maintenance — ideally, this should be tool-less as the easier it is to remove, the more the user is likely to clean the piston and cylinder.

The second concerns the dust cover — the second upper we got handsy with had no issues, but we’d like to see some long-term testing of multiple units before giving it the thumbs up.

In all, Brownells has come up with a useful piston upper, which offers great functionality for those looking for a suppressor host. They’ve managed to do this without creating something excessively muzzle heavy — the piston system adds very little mass and in the 9-inch 300BLK version, it’s hardly noticeable. Given the ability to mount a folding stock, it’s worthy of consideration for your next backpack or truck gun. 

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