This special, limited-production model of our popular BRN-180S complete upper receiver comes with a premium Primary Weapon Systems FRC Rearden flash hider permanently pinned and welded onto the barrel to meet the National Firearms Act's (NFA) requirement for a minimum 16" barrel length. This gives you the shortest-possible barrel without having to apply to the ATF to register your rifle as an SBR. You actually get TWO benefits because this PWS flash hider also serves as a quick-attach mount for sound suppressors that use the Rearden, Atlas, and Plan B mounting interfaces.

Designed in conjunction with Primary Weapons and Foxtrot Mike, the Brownells BRN-180S Complete Upper Receiver is part of our extensive BRN-180 line of AR-15 compatible gas piston uppers, which was inspired by the highly advanced Armalite AR-18 / AR-180 rifles of the 1960s. The BRN-180S shares a large chunk of its components with the standard BRN-180 upper, but it includes key features to improve reliability and usability with a shorter barrel.

The BRN-180S's adjustable gas block can be switched between two settings, simply by flipping a small lever: "S" is for use with a sound suppressor, "U" for normal, unsuppressed fire. The lever is easy to access through a convenient cutout in the handguard.

With an entirely self-contained recoil system, the BRN-180S can be mounted to a standard "mil-spec" AR-15 lower receiver without a buffer tube. This enables easy compatibility with folding stocks and adapters for stocks that mount to M1913 Picatinny rails. The recoil guide rods and buffer easily are easily removed when the upper receiver is separated from the lower. The bolt and carrier slide out when you remove the charging handle at the rear. A large ejection port gives you easy access for cleaning. We also offer dedicated BRN-180 Lower Receivers that come with an integral Picatinny stock attachment rail.

The lightweight-profile barrel is almost entirely encased by the slim M-LOK handguard, making for an extremely lightweight package, even with the piston-driven operating system. The full-length Picatinny top rail sits extremely low compared to other piston-operated AR-15s, giving you the benefit of broad compatibility with common AR-15 height optic mounts and sights. This barrel features a .223 Wylde chamber that is optimized to deliver excellent performance from the broadest spectrum of .223 Remington and 5.56x45mm NATO ammunition.

The free-floating M-LOK handguard can be removed simply by taking out one large screw located on the underside of the receiver. This screw engages the rear of the barrel, pulling the handguard tight up against the receiver, making the handguard an extremely strong, stable optic and accessory mounting platform that won't whip, wobble, or rotate. At the same time, this handguard is very easy to remove for quick access to the BRN-180 gas system.