BRN-180SA(R) Gen2 - Now with 300 Blackout Configuration! Designed in conjunction with PWS & FM Products, the Brownells BRN-180SA(R) Complete Upper Receiver is the newest iteration of the BRN-180A(R) Upper Receiver, which was inspired by the ArmaliteA(R) AR-180 of the 1960s. The BRN-180SA(R) shares a large chunk of components with the BRN-180A(R), but introduces key features to improve reliability and usability in a short configuration. The BRN-180SA(R) is obviously shorter than the standard BRN-180A(R). The 300 Blackout required a shorter system to ensure reliability with a wide variety of supersonic and subsonic ammunition. This resulting shorter system also required a Mfg: Brownells