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Review: BRN-180S Gen2 300 BLK Complete Upper Receiver

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Brownells has introduced a product almost guaranteed to sell: The BRN-180S Gen2. What is it? Well, it’s a complete upper pistol assembly (receiver) based on the AR-180, chambered in .300 BLK, that fits any current Mil-Spec AR-15 pistol lower. What’s so great about that? Plenty.


The AR-180 was the civilian version of the AR-18, which itself was a scaled down version of the 7.62 NATO-caliber AR-16, Eugene Stoner’s last design at ArmaLite. The company sought to create an easier-to-produce, more-affordable, small-caliber rifle built from stamped and welded sheet metal rather than machined forgings, and one that didn’t violate the AR-10 and AR-15 production rights ArmaLite had sold to Colt. Downsizing the AR-16 fell to subsequent ArmaLite Chief Designer Arthur Miller.

The gun Miller eventually produced evinced both reliability and accuracy. It relied on a short-stroke gas piston located above the barrel. It was similar to the AR-15/M16 in some ways (seven radial locking lugs), but different in others (recoil springs in the receiver rather than a buffer tube in the buttstock). However, the AR-18 and civilian AR-180 could use standard AR-15/M16 accessories. Various editions of the guns were produced in fits and starts, but it was basically a stepping stone to other designs rather than a final destination.

Upper Hand

There are several advantages to buying just the upper. First off, it saves you the cost of buying a complete gun. Perhaps just as importantly, you get to keep using a lower with which you are already familiar and maybe have already customized. Moreover, it allows you to swap back and forth with your original-caliber upper while using the same magazines and accessories.

The versatility doesn’t stop there, either. The .300 BLK, with available subsonic loads, is great for suppressed use. The BRN-180S Gen2 is especially good for it as it’s cut-out handguard and two-position gas system assure best functioning with the can/ammunition combination of your choice. If you’re looking to hunt, installing the .300 BLK upper allows you to go afield in those places that prohibit big-game hunting with .223 Rem. or 5.56 NATO chamberings. Of course, having a second ammunition option is especially important now that ammunition is so hard to find.

The first thing that impresses about the BRN-180S Gen2 is the quality. Yeah, the original gun on which it was based had thrift as an impetus to creation, but if you expect the BRN-180S Gen2 to be cheaply made and of poor quality, guess again. This is a well-made, well-finished piece of gear. No lower is diminished when paired with this upper. We put it on The Saint pistol, from Springfield Armory. It made for a good, snug fit and performed solidly.

As previously mentioned, the gas system is a user-friendly design that largely obviates disassembly to make adjustment to the gas system, thanks to the cut-out in the M-Lok-compatible handguard. If you do need greater access to the gas system, though, removing the handguard is less problematic than ever before, as a new design retains the handguard with a single locking screw. The company says the system is both simpler and more secure, with improved rigidity.

A Picatinny top rail supplants iron sights, allowing you to install your own irons, an optical sight or both. The muzzle device is a three-prong flash hider that replicates that of the AR-180. It has a solid bottom piece that doesn’t stir up dust when you fire the gun from the prone position. The muzzle is threaded at 5/8-24 tpi, so you can install different devices, including brakes and suppressors.

Both the bolt and the 4150 carbon steel barrel are black nitrided, which improves hardness, lubricity and corrosion resistance. Operating on twin guide rods, the bolt carrier travelled smoothly during testing. A steel plate with polymer buffer is apparently are built into the upper. The big advantage to this design is that it allows for use of a folding brace, if so desired. In fact, Brownells is now offering the unit with a folding brace for an additional $160.

After installing an unmagnified red-dot sight, we noticed the s-shaped, reciprocating bolt handle, tipped with a knurled, cylindrical head, very nearly touched the head of the sight-base screw. It didn’t, but it came close. Everything worked fine in our setup, but be aware you may have to move your sight a slot or two to clear the bolt handle.

When the bolt is released and goes into battery, it doesn’t do so with the same authority as an AR-15. At least it didn’t feel like it, although it functioned just fine. The only glitch we experienced in testing was once, when the bolt had locked back after the last round in the magazine had been fired, the bolt came forward on its own as the magazine was removed.

We tested the BRN-180S Gen2 with three different weights and brands of ammunition. It fed and fired everything without incident, even when we mixed loads in the same magazine. Ejection was satisfactory and consistent. Point-of-impact changes were fairly severe, not completely unexpected when some projectiles weighed literally twice as much as others and some loads were intended to be subsonic while others were created to go supersonic.

Fliers opened up several otherwise outstanding groups. Often, three or four shots clustered so closely that they touched.

There’s a lot to like about this unit. You may find the price point kind of high. We did. On the other hand, we were pleasantly surprised by the quality and, these days, it’s getting harder and harder to find a good AR-based firearm for less than $1,000. If you’d like to increase your shooting options to include suppressed shooting or big-game hunting and want to continue using a lower you’ve put in time with, or if you want to improve your chances of finding ammunition during the current shortage or the next one, the BRN-180S Gen 2 is a pretty sound option.

BRN-180S Gen2 300 BLK Complete Upper Receiver

  • Manufacturer: Brownells (in conjunction with PWS and FM Products); (800) 741-0015, brownells.com
  • Action Type: Short-stroke, gas-piston semi-automatic
  • Caliber: 300 BLK
  • Barrel Length: 10 inches
  • Rifling: 1:8 inches
  • Receiver: Hardcoat-anodized 7075 T6 aluminum
  • Sights: None; Picatinny top rail
  • Weight: 58 ounces
  • MSRP: $899.98

Shooting Results

                                                                    Velocity (fps)             Group Size (inches) 

                                                                                                Smallest        Largest Average

Barnes 110-grain VOR-TX TAC-TX FB                 2,220                .7                     1.4       1.1

Win. 200-grain Open Tip – Range Subsonic     1,050                .7                     1.7       1.3

SIG Sauer Elite 220-grain Subsonic                 1,003                1.4                   2.3       1.7

Velocity measured in fps 10 feet from the muzzle for 10 consecutive shots with an Oehler 36P chronograph. Temperature: 71 degrees Fahrenheit. Accuracy measured in inches for five consecutive, 5-shot groups at 50 yards from a rest.

Article by Daniel T. McElrath


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