November 22, 2023
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Brownells has seen a lot of success with their BRN-180 line, a slightly modernized/altered version of the classic AR-180 design, and their newest version, the 300 AAC Blackout (300 BLK) BRN-180SH, nicknamed the “Hush Puppy” in-house, is quite interesting. If you haven’t been keeping up, here’s just a brief bit of history. The original select-fire ArmaLite AR-18 was designed by Arthur Miller with assistance from Charles Dorchester, L. James Sullivan, Tom Tellefson, and others. The weapon was derived from Eugene Stoner’s AR-16 (7x62x51mm “father” of the AR-18), in the early 1960s, as an economical alternative to the M16 after Colt took over that ArmaLite product. Unlike the direct-gas-impingement M16, the AR-18 uses a short-stroke gas-piston system. The semi-auto civilian version of the design was the AR-180. That rifle Arnold uses in the original Terminator movie? It's an AR-18, not an AR-15.
The BRN-180 Line
Brownells originally started with BRN-180 upper receiver assemblies meant to mount on standard AR-15 lowers, but as one of the advantages of the design is all the moving parts are inside the receiver, the design can be fitted with a folding stock. Brownells now offers lower receivers with MIL STD 1913 rails on the back to accept side-folding stocks. They’re styled like the original AR-180 lowers, but they take AR-15 internals. Brownells offers BRN-180 uppers in 5.56x45mm NATO, 300 BLK, and 7.62x39mm in various barrel lengths. The 300 BLK BRN-180SH (for ‘shhhh’) is the same, but different. The standard BRN-180s have a two-position gas system. Through a slot in the handguard, you’ll see where it can be adjusted. You can use the provided tool to adjust it, or the tip of a cartridge works pretty well, too. There are two well-marked settings, “1” and “2.” You can swap between them for whether you’re shooting suppressed or unsuppressed. You choose what works best for you. But the BRN-180SH adds a third position to the gas system, marked with an “X.” Switching to X completely shuts off the gas to the piston, and it won’t cycle at all. Here we get to the Hush Puppy nickname.
If you’re a bit younger, you might not have heard of the Hush Puppy. I’m not talking about tater tots or comfortable shoes for senior citizens, but rather a specialized pistol developed during the Vietnam War for eliminating sentries and guard dogs (hence the nickname ‘Hush Puppy’). Suppressed guns are quiet, but almost never Hollywood quiet, even with subsonic ammo. The Hush Puppy was a Smith & Wesson Model 39 9mm developed for the U.S. Navy SEALs during the Vietnam War, officially known as the Mk 22 Mod 0. It was equipped with a suppressor and tall sights that could be seen over the suppressor, and later versions were fed by a double-column magazine and were the basis for the subsequent Model 59. But what set the Hush Puppy apart was the lock that prevented the slide from cycling when fired. This eliminated the sound of the cycling slide and any gas shooting out of the ejection port, getting the pistol closer to that “Hollywood quiet” goal.
Right now, the BRN-180SH upper is only available in one configuration, a 10-inch-barreled upper chambered in 300 BLK. The thing that makes this upper immediately identifiable is the new charging handle design. Instead of the original bolt handle that has a dogleg and sticks up and out, the 180SH has a lower profile handle that juts down and forward as it’s shipped from Brownells. According to Brownells, the handle was redesigned to be more easily used in single shot mode with the gas shut off. With a 10-inch barrel, you are relegated to using it on a registered short-barreled rifle (SBR) or AR pistol. As I write this, yet another federal court has issued a preliminary injunction, staying the ATF’s rule against pistol braces in its entirety while it is challenged in court. The first such ruling specifically exempted the plaintiffs in that lawsuit, which included members of the Firearm Policy Coalition, of which I am one, so you’ll see my build with this upper proudly sports a pistol brace.
The barrel free-floats inside an aluminum handguard that leaves about an inch of barrel exposed. The handguard has M-LOK attachment slots all around, and there is a MIL STD 1913 “picatinny” rail along the top, only interrupted for the gap where you are meant to access the gas system. According to Brownells, the barrel has a 1:8-inch twist and is threaded 5/8x24, which is the standard thread pitch for 300 BLK barrels, so my plan was to use my Silencer Central Banish 30 suppressor for testing. But that didn’t work out. The barrel (at least on my sample) was actually threaded 1/2x28, which is the standard thread pitch for 5.56 barrels. Then an adapter was attached to the barrel with 5/8x24 threads on the exterior and an A2-style flash hider was attached to the adapter. But I could not separate the flash hider from the adapter, nearly breaking a finger in the attempt, so I had to go with the ½x28 threads on the barrel. For testing, I used a Silencer Central Banish 45 can, which is the only one I had on hand which had that direct thread pitch rate. Not the most efficient can for the 300 BLK, but it worked just fine for comparison testing.
The BRN-180SH upper is designed to fit on standard AR-15 lowers, and it does, although it doesn’t look quite right; it’s a bit humpbacked. For this project, I thought it only fitting to use one of Brownells’ BRN lowers. They offer a forged or a more expensive billet model. There isn’t a lot of difference in appearance, and I chose to go with the forged model. It takes standard AR-15 internal parts with the main difference being the external dimensions of the receiver. The magazine well is shorter and angled. The trigger guard is curved and made to look like a piece of stamped steel, and the rear of the receiver has a different profile because of the rail back there. The only real issue I found was with the different profile of the receiver behind the pistol grip. The BRN-180 lower is designed to accept AR-15 pistol grips, but because of the different receiver profile, any pistol grip with material under the web of your hand will likely not fit, at least not without some trimming with a file or a Dremel tool. Standard A2 pistol grips fit just fine, but I hate them, so I hacksawed off the back of a Magpul K2 grip and mounted it to my lower. The end result looks exactly as good as you’d expect if a hacksaw is your main gunsmithing tool. I’m still looking for a more permanent solution. At the back of the pistol, I mounted a JMac Customs arm bar with a Gear Head Works Tailhook brace. With the brace folded, this piece is only about 20 inches long.
Hushed Range Time
I have a few comments about the 300 BLK cartridge and gas-piston guns. With a standard DI AR-15, if you want to switch between hot supersonic and soft subsonic loads, you’ll probably need to change out your buffer to ensure reliability. Gas-piston guns, on the other hand, usually don’t care. The gas travels a shorter distance to the piston head, and so while you might want to change your gas settings, you won’t have to. I first tested the gun with the provided flash hider. On gas setting 1, my BRN-180SH upper cycled flawlessly with every kind of super- and subsonic ammo I had. Recoil was as expected, and the BRN-180 system cycles smoothly. FYI as the 300 BLK cartridge is optimized for a 9-inch barrel, out of this 10-inch barrel, you’ll get full velocity out of subsonic loads and 90 percent of the advertised velocity for supersonic loads. I did rough accuracy testing, and most loads would do one to two-inch groups at 50 yards just using an Aimpoint RDS. Officially, the gas settings are suppressed, unsuppressed and off, but depending on whether you’re using super- or subsonic ammo, and what brand, your functional use may differ.
To be honest, I just don’t see how this bolt handle works better for cycling by hand than the original, which sticks out farther from the receiver and thus a bit easier to grab. However, this handle can be adjusted. It can stick up or down, whichever you choose. To change it, you have to pull it out of the bolt, and on the inside of the handle there’s a screw you have to loosen, so you can rotate the handle to point in whatever direction you prefer. With the gas system shut off (‘X’ setting) the gun worked exactly as advertised. It didn’t cycle at all, so it was a bit quieter. If you can think of a reason or situation where you’d want a single-shot 300 BLK that doesn’t spit brass, suppressed or otherwise, the BRN-180SH delivers on that setting and on every other gas setting.
The good news is that this upper receiver is more universally reliable with any kind of 300 BLK ammo than the average AR-15, due to its short-stroke gas-piston operating system. It addresses the main weakness of a 300 BLK AR-15, which is the ability to shoot every kind of ammo without swapping parts. The bad news? That short-stroke gas-piston operating system is inherently louder when suppressed than a standard direct gas impingement AR. With that gas piston, the gas flows up from the barrel, hits the head of the piston and gets it moving. Once that piston has moved a certain distance (far enough to ensure cycling), it clears a secondary port which vents the excess gases. In this case, it’s inside the handguard. That venting port adds a bit of noise, so the Brownells BRN-180SH, even on single shot, is not as quiet as the Hush Puppy nickname would indicate. The BRN-180SH upper receiver assembly has an MSRP of $999.99, but currently Brownells has them on sale for $899.99. The BRN-180 forged stripped lower receiver I used is $99.99. After that, all you need is a lower parts kit and a brace/stock. As AR builds go, this is not that expensive, but it’s a remarkably unique system.
Brownells BRN-180SH Upper Receiver
- Type: Complete upper receiver
- Cartridge: 300 BLK
- Barrel: 10 in., 1:8-in. twist
- Finish: Hardcoat anodized
- Handguard: M-LOK
- Gas System: 3 position
- Muzzle: 5/8x24 threaded, A2 flash hider included
- MSRP: $999
- Manufacturer: Brownells
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