BRN-4® UPPER RECEIVER ASSEMBLIES

Assembled from All New Components – Fits Standard AR-15 Lowers The BRN-4® Upper Receiver is now available as an Assembled Upper, with Barrel and Gas System installed. Simply add your preferred HK® 416 compatible handguard and any 1/2-28 muzzle device, and you’re ready to hit the range! Built from the ground up, the core of the BRN-4® Upper Receiver is an all new Bolt Carrier Group, featuring a slick nitride finish. The carrier itself is machined from one piece of forged 8620 steel. The bolt is precision machined from 9310 tool steel and headspaced prior to and after barrel installation. The new BRN-4® barrel, produced by Faxon®, is available in a variety of profiles and lengths to suit your needs. Barrels are chambered 5.56x45mm NATO, are button rifled with a 1-7 twist, 1/2-28 muzzle and come with the appropriate gas block for a given barrel length. Barrels are available in a medium or heavy profile. The heavy profile ensures a rigid and robust platform for precision shooting. The medium profile balances the desire to have a lighter piston configuration, while still having plenty of barrel material to prevent drifting of grouping as the barrel heats. The upper receiver utilized in this assembly is made completely new, from billet, to mirror the profiles commonly found on forged upper receivers. Contours of the upper are entirely machined from billet, so rounded areas such as the cam pin protrusion and complex contours will show machine passes more prominently. The machined upper is finished with matte black hard coat anodizing. The proper piston bushing is installed to eliminate any piston wear on the aluminum part, and is secured in place with blue threadlocker. The BRN-4® features much longer barrel nut threads, engaging the barrel extension over a much larger surface area than a standard AR-15. This ensure that the barrel is rigidly mounted with the pre-installed barrel nut. Barrel nut is torqued properly with AeroShell Grease 64 applied to the upper receiver threads. The barrel nut is reinstalled 3 times to ensure an accurate torque spec is achieved. Gas blocks are vented forward, to reduce gas sent rearward into the system, and are mated specific to the 10.4 or 14.5/16 inch barrel lengths. Upper includes Magpul ejection port cover and mil-spec charging handle. Handguard installation is extremely simple, just slide handguard over the barrel and tighten one bolt. Be sure to follow any specific instructions advised by the manufacturer. Muzzle devices installation is also straightforward, as the barrel is 1/2-28 and the BRN-4 upper is compatible with common upper receiver “rods” and jigs. Any AR-15 1/2-28 muzzle device will be compatible. Brownells recommend H1 or H2 recoil buffer with carbine recoil spring for optimal operation.