I've exhausted sources at old.ar15.com and biggerhammer.com. A friend has an upper with a BM barrel, but I don't think the upper is a bushie. It has no forging  marks anywhere, including on the take down pin area nor does it have the grey dry lube bushy uses inside the upper. There are no marks anywhere on the upper I can tell. Logically it could be made in the same factory as the bushy..but how do I know? who all makes them?