Out of stock
SKU: 78000599
UPC: 050806113510
The Brownells BRN-180S Gen 2 upper receiver assembly brings the legendary AR-180 operating system into a modern, compact package for shooters who want piston-driven reliability without proprietary lower receivers. Chambered in .223 Wylde to handle both 5.56 NATO and .223 Remington with equal precision, this 10.5-inch barreled upper drops directly onto any mil-spec AR-15 lower in our lowers inventory. Designed in partnership with PWS and FM Products, the Gen 2 iteration refines the original concept with improved internals and a shorter handguard configuration optimized for suppressor use and close-quarters handling.
The short-stroke gas piston system eliminates the fouling and heat transfer issues inherent to direct impingement designs, running cleaner and cooler during extended strings of fire. A two-position adjustable gas block lets you tune the system for standard or suppressed operation without tools. The 4150 carbon steel barrel features a nitride finish for corrosion resistance and carries a 1:8 twist rate that stabilizes projectiles from 55 to 77 grains effectively. The dual guide rod system with integrated polymer buffer and steel plate means no buffer tube is required—making this upper ideal for folding stock configurations. The free-float M-LOK handguard accepts accessories at three, six, and nine o'clock positions, while the three-prong flash hider pays tribute to the original AR-180 aesthetic. Standard AR-15 extractors and a nitride-treated bolt complete the assembly.
This upper excels in truck gun builds, backpack configurations, and any application where a folding or non-extending stock matters. The 1/2-28 threaded muzzle accepts standard .223/5.56 muzzle devices and suppressors. Made in the USA, the BRN-180S Gen 2 pairs naturally with AR pistol lowers for a compact defensive platform or with SBR-registered lowers for a folding rifle setup. Browse our complete firearms selection and 223 Wylde-compatible ammunition to build out your kit.
No. The dual guide rod system with integrated polymer buffer and steel plate contains the recoil assembly entirely within the upper receiver. This allows you to run folding stocks, side-folding braces, or no stock at all without any buffer tube extending into or behind the lower receiver.
The BRN-180S Gen 2 upper fits any standard mil-spec AR-15 lower receiver. No proprietary lowers or adapters are required. It attaches using the standard front and rear takedown pins found on all AR-15 pattern lowers.
Yes. The .223 Wylde chamber is specifically designed to safely fire both 5.56 NATO and .223 Remington ammunition while optimizing accuracy for both pressure levels. The 1:8 twist rate stabilizes bullets ranging from 55 to 77 grains.
The two-position adjustable gas block switches between standard and suppressed settings. When running a suppressor, the reduced gas setting prevents over-gassing and excessive bolt speed. The adjustment requires no tools and can be done in the field.
The muzzle is threaded 1/2-28 TPI, which is the standard thread pitch for .223/5.56 caliber muzzle devices. This accepts most flash hiders, muzzle brakes, compensators, and suppressor mounts designed for AR-15 rifles in this caliber family.
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