BRN-4 UPPER RECEIVER BUILD KITS

Build your own upper receiver kit! The BRN-4® is now available as an Build Kit. Simply add your preferred HK® 416 compatible handguard and any 1/2-28 muzzle device, and you’re ready to build! Includes all of the main components, plus a BRN-4® barrel nut wrench to properly install the barrel. 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 BRN-4® features much longer barrel nut threads, engaging the barrel extension over a much larger surface area than a standard AR-15. For barrel nut installation, Brownells recommends 50-80 ft/lbs of torque, using the included barrel nut wrench. Simply insert the barrel into the upper receiver, apply grease or anti-seize to the upper receiver and barrel nut threads (we recommend AeroShell Grease 64, 430107078 or Copper Anti-Seize, 083000044), thread on barrel nut, attach wrench to barrel nut using the two screws on the wrench, and then apply torque using a 1/2" torque wrench. 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. Be sure to use a proper bench block and punches when installing gas block coil pins. Coil pins can be installed using punches and a hammer, or pressed in. 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. Upper includes Magpul ejection port cover and mil-spec charging handle. Brownells recommend H1 or H2 recoil buffer with carbine recoil spring for optimal operation.