I am thinking of a 9mm AR. So far this is what I understand (...I think)

1.  If I wish to use sten mags I can use any lower but will need the olympic upper w/the Hahn sten adapter.

2.  If I wish to use colt, uzi, or promags, I can use any lower, but I need to use a Rock River or Bushmaster upper.  Does the use of the RR or BM require a Hahn adapter, or do these mags fit the receiver directly?

Thanks

colt style system requires a mag block.