BCM and compatibility questions

[Stepaway]

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.

[Constructor]

I do not know who machines BCMs uppers or lowers and as far as I know there is no compatability chart.

[RainierArms]

You shouldn't need a compatibility chart as most AR15 parts are interchangeable. There are times when you have a in-spec upper and and in-spec lower that will not even fit together. Since milspec calls for a certain amount of tolerance, if they are both at the opposite end of the spectrum, it may not work well together. You can have one set fit perfectly and another set be a rattle can or something so tight you need a mallet to put together. As stated before, I've had a very reputable company's upper & lower that didn't even fit together.