BRN-4 Stripped Lower Receiver, machined from original HK416™ forging out of Germany. Brownells started with a raw HK416™ forging, and had them machined by Primary Weapons Systems to be as authentic as possible. These lowers feature the classic contours of the HK416™, found on no other lower receiver. Selector markings are inspired by HK416™ markings, with color filled pictogram markings. The FFL information is machined on the front of the magazine well, where the normal HK416™ warning information is placed. Following machining, these receivers get a matte black Type III anodizing. The BRN-4 is compatible with all standard AR-15 components, and is right at home on an HK416™ build or a custom AR-15. Not compatible with Surefire 60/100rd magazines, Magpul Gen 1 or 2 PMAGs, Tangodown Magazines or Hexmags. This is due to the original profile of the HK 416 forging.