Yeah, I think that I wouldn't get to indepth with all the different clones out there. AR's are like AK's the variants and possiblities to mix and match most parts of one with another are endless. I would maybe note that some are not interchangable in certain areas. Like the non-law enforcement/military only Colt AR-15's that had larger holes in there receivers so you could only use Colt's parts. Or how some of the later Colt Match Target series had a auto sear block pinned in them to prevent you from putting in a auto sear. I would only add this because it makes the weapon less convertable to auto fire. Or if someone in the group is not a machinist who can make spare parts, it becomes worthless, if parts get damaged, lost, or worn out.
On a side note it's funny how the artist for the original Twilight 2000 Small Arms Guide used a Colt SP-1 for his model of a M-16A2 (atleast I believe he did). You can see the SP-1 written on the reciever and the front take down pin on the lower receiver has a screw instead of just the push pin.
