BRN-4A(R) UPPER RECEIVER ASSEMBLIES WITH CHROME LINED BARRELS Assembled from All New Components - Now with Chrome Lined Barrels. Fits Standard AR-15 Lowers. The BRN-4A(R) Upper Receiver is now available as an Assembled Upper, with Barrel and Gas System installed. Simply add your preferred HKA(R) 416 compatible handguard and any 1/2-28 muzzle device, and you're ready to hit the range! Available in barrel lengths of 10.4, 13.7, 14.5, and 16 inch, these upper receiver groups are suitable for any need. Also available in standard and heavy profiles. Chrome lined bore and chamber of these barrels has been the go-to for h Mfg: Brownells