Can you tell me who makes BCM lowers - I searched this forum, the Black rifle forum and didn't see the answer on their website. They appear to sell a lot of LMT equipment but I'd like to know for certain. Second question, is there true compatiblity among the manufacturers of uppers and lowers or is there some cross reference you can point me to that would identify compatability problems? I want to make sure when I buy my first AR that I have made a choice that will keep my options open in the future. Thank you for your time and patience.