Just submitted an Eform 1 to SBR an American Defense Mfg lower. I'll be using it for steel challenge (9mm) and home defense (300 blk). The 9mm configuration will use a CMMG upper and Endomags which run great in my 16" barrel CMMG 9mm upper. It's a great approach to have a single lower for 9mm, 5.56 and 300 blk. Can't wait.