Fans of the versatile 300 AAC Blackout cartridge should take a good look at Brownells latest update of the classic AR-180 platform. The BRN-180 GEN 3 series of rifles/pistols have several improvements. When Brownells first introduced their BRN-180 in 2019, they switched the receiver material from steel to aluminum, engineered upper and lower compatibility with standard mil-spec AR15 uppers and lowers, used standard AR15 fire control and magazine parts, free floated the barrel inside an aluminum M-lok handguard and topped the rifle with Picatinny rail end to end.
BRN-180 GEN 3 New Features
They retained the AR-180 short stroke piston operation which allowed for a folding buttstock, and its peculiar dogleg reciprocating charging handle. It was a nice gun. While no fan of exposed parts flying back and forth, I liked that on the BRN-180. It could be made more compact with a folding stock and could be fired in that manner too. Its short stroke piston operating system would let it run cleaner and cooler with a suppressor than a direct impingement operated AR-15. The latter blew back too much gas through the action and into my face to be fun. The BRN-180 GEN 3 guns, and especially the 300 Blackout pistol, are optimized for suppressor use.
The GEN 3 guns have a lot of notable new features. The charging handle is now non-reciprocating and mounted on the left side of the receiver with a downward angled handle to help keep your hand clear of your rail mounted optics. The possibility of outside dirt and debris intruding into the upper receiver is now virtually eliminated by a rubber curtain sealing around the charging handle slot and an automatic ejection port cover mounted to the bolt that seals off the rear of the receiver when the bolt is in battery.
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New Handguard
The new free float front handguard mounts more rigidly to the upper with just a single set screw which simplifies its removal and installation. I found it extremely rigid with virtually no apparent flex. It also has integral, steel lined, QD sling mounting sockets on the left and right side. These are the type that don’t allow the swivel base to rotate all around in the socket. It seems like a small thing, but stabilizing those swivel bases lets you position the swivel loop in a way that it won’t contact the aluminum handguard and make noise or scratch up the anodizing.
The one drawback of this new front handguard is that only the bottom, and most important, row of M-Lok slots is readily useable for mounting accessories. The interior ribs that stiffen the handguard prevent the “T” locks used to mount M-Lok accessories from fully engaging the slots in the rows along the sides. This could be remedied by altering the geometry of the “T” locks so they reach over the ribs.
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What’s On The Inside?
The guts of the rifle no-long get launched out when you separate the upper from the lower. On GEN 3 guns, the bolt carrier, guides and recoil springs now stay in place when the upper is tilted open thanks to a clever sliding retaining latch mounted at the back of the assembly. That being said, it’s still a bad idea to cycle the bolt with the upper dismounted. The retaining latch is metal, but the hook in engages with on the guide rod base is plastic.
Improvements to longevity and function include new stronger, rectangular, wire recoil springs, a steel cam guide screwed onto the inner left side of the upper receiver to protect the aluminum from wear and tear, a steel case deflector behind the ejection port, and an anti-bounce bolt that prevents light firing pin strikes by ensuring the bolt stays fully into battery after each shot.
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All these improvements are great, and I especially like the SIG-MCX platform style steel reinforcement of the aluminum upper receiver, but I’ve saved my favorite GEN 3 upgrade for last.
Easy Adjust Gas System
The GEN 3 guns have the new Easy Adjust Gas System that allows you to change the gas flow into the piston by reaching your fingertip through the access opening in the handguard and moving the selection lever. A viewport in the top the handguard shows the lever position number. There are three settings on the .223 guns and four for the 300 Blackout pistol. With 300 AAC blackout’s wide range of bullet weights and pressures, you could make an argument for more settings, but four is better than three.
Position 1 is for suppressed supersonic loads of 150 grain bullet weight or less. The position 2 is for unsuppressed supersonic loads with bullets from 110 to 150 grains. While position 3 is for suppressed subsonic loads between 190 and 225 grains and light supersonic loads. Position 4 is for unsuppressed shooting of subsonic loads with 190-225 grain bullets weights in adverse conditions.
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Getting It Dirty
In theory, the gas adjustment is supposed to be toolless, but in practice I found it took only a handful of subsonic rounds to lock up the lever with carbon. Initially this was easily remedied with a few drops of bore solvent applied to the value body joints. As the valve got dirtier, I really couldn’t move the lever with my finger at all. Freeing it up required taping the lever right or left with a wood dowel and an improvised mallet. A better solution was just removing the spring loaded lever and taping the valve body straight inward with the wooden dowel. Adding a few drops of solvent helped.
This semi-toolless adjustment was a little disappointing, but hardly a big deal. I’d rather carry a wood dowel than an extra buffer, and it didn’t seem to manifest itself when shooting anything unsuppressed or when shooting supersonic loads suppressed. There is no need to remove the handguard, or even the suppressor in most cases, to free-up the lever when it gets stuck.
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Because this is just an upper receiver, I had a lot of options to build it up for shooting. The Brownells online catalog is so extensive, it’s about the closest thing to one-stop shopping. I already had the now discontinued original AR-180 style BRN-180 lower receiver into which I installed a Luth AR lower parts kit, Rise RA-535 Advanced Performance drop-in trigger, Lewis Machine Tool rubber overmold pistol grip, MagPul PMAG20 GEN M3 magazine and a. a Midwest Industries side-folding buffer tube stock base with a five-position SB Tactical SBA3 pistol stabilizing.
Optics, Light & Laser
I had a personal defense/bug-out/emergency hunting role in mind for this pistol so a folding brace was important to keep it compact. This also influenced my sighting choices. The MeproLight M22 Pro reflex sight is an enhanced version of the military M22 that has a battery powered back up for that model’s standard fiber-optic/tritium powered reticle. This alleviates reticle washout when shooting from area with low ambient light while aiming into a brightly lit area. (ex. shooting outdoors from indoors).
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The battery lasts up to 50,000 hours, and the tritium lasts ten years, but it can run forever to a greater or lesser degree without either thanks to the fiber optics. The 3.5 MOA dot and 40 MOA circle Bullseye reticle gives me some long rangeaiming points to compensate for bullet drop. I added a Bushnell 4X magnifier to improve long range accuracy. It can be flipped to the side to use the M22 Pro unmagnified.
For extremely close range sighting and night use, I added a Streamlight TRL-RM1 Laser G combination tactical light and green targeting laser. The 500 lumens; 11,000 candela; light has a beam range exceeding 200 yards, runs 1.5 hours on a CR123A Lithium battery, has a strobe feature, and is IPX4 water-resistant. It also serves as a hand-stop to keep my fingers away from the muzzle when shooting the pistol unsuppressed.
Suppressor & Sling
To quiet it down to ear-safe levels, I used a direct thread 9-inch Silencer Central Banish 30 multi-caliber suppressor. My neighbor never even noticed I was shooting when I fired sub-sonics.
At this point, the gun was getting heavy and I realized a second sling attachment point at the rear of the receiver’s Picatinny rail was needed to carry it folded. The Magpul RSA QD rail sling attachment was perfect for the job. Like the sockets on the handguard, it permits only minimal movement of the sling swivel base.
Accuracy On The Range
I did my accuracy testing at 50 yards, firing from the bench with the pistol’s forend and brace well supported. All loads were fired with the suppressor attached and using the 4X magnifier. I’ve found 300 AAC Blackout to be exceptionally accurate from short barrels in the past, and the BRN-180 bore this out again.
Supersonic Winchester Deer Season XP 150 grain Extreme Point hunting loads averaged 1,651 feet-per-second (FPS) with five shot groups averaging 1.35 inches. Subsonic Lehigh Defense monolithic copper alloy 194 grain Maximum Expansion hollow points averaged 1,017 FPS and groups of 1.10 inches. These bullets are precision lathe turned and more internally and dimensionally consistent than traditional cup and core jacketed bullets. Its ogive is partially cut so that it consistently opens up on impact with tissue turning the projectile into something resembling a miniature airplane prop many times its original diameter that chops a large wound cavity as it moves through the target.
Subsonic Black Hills Ammunitions 220 grain Open Tip Match bullet averaged 982 FPS and groups averaging 1.56 inches.
Throughout testing function was smooth with no failures of any kind. Supressed subsonic loads were fired with the gas value in position #3. For the suppressed supersonic load I used the #1 gas value setting. All cases were clearly striking the deflector on ejection and ultimately landed in the 4 o’clock position with the subsonics and the 5 o’clock position with the supersonic load.
At The End
Though I built this pistol with a BRN-180 lower receiver with an integral Picatinny rail section at the rear, all the BRN-180 uppers will fit on any mil-spec AR15 lower. Brownells currently offers an AR15 style lower for their BRN-180 with ambidextrous controls and a rear facing short Picatinny rail section for stock attachment for $299.
Specifications: BRN-180 GEN3 (9 inch barrel) Upper Receiver
- Caliber: 300 AAC Blackout
- Capacity: standard AR15 magazines
- Operation: semi-auto, short stroke piston
- Barrel: 9 inch, 1:6 twist, recessed crown, 5/8″-24 TPI threaded muzzle with A2 flash hider, four position adjustable gas valve.
- Overall length: 17.38 inches receiver alone, 33.38 inches as configured with folding brace fully extended & 26.25 inches with brace folded.
- Weight: 3 pounds 2.8 ounces receiver alone, 8 pounds 12.4 ounces as configured with empty 20 round MagPul PMAG GEN M3 magazine.
- Lower Receiver: BRN-180 lower (now available only in traditional AR15 layout.)
- Finish: black anodized aluminum
- Stock: SB Tactical SBA3 pistol stabilizing brace on Midwest Industries (MI-STAP-SF) side folding six position buffer-tube style stock.
- Trigger: drop in, single stage, 3.5 pound pull, Rise RA-535 Advanced Performance
- Sights: none, tested with Meprolight M22 PRO & Bushnell 4X magnifier.
- MSRP: $1,199 for complete barreled upper receiver assembly.
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