A while back Tweak (one of the moderator's here, and over all AR Guru (both on AR15-L and MD-AR15.com) actually sent FN a letter and asked them about the parts.
FN responded and the letter is in the File area of
[email protected]. Just sign up as a member to the e-mail list (you don't even have to get the e-mail as it can be read online), and you can read the correspondance.
BTW I did post FN comments here and they indicated they do not sell to anyone other than the .MIL types.
Now there are companies that do get forgings and sometimes machined parts from some of the same vendors that FN does. These still are not FN parts contrary to many 'bottom feeder' claims - FN has never taken possession of the part nor have they machined the forgings, or even done their in-house Quality Inspection.
The interesting thing is the vendors that do supply FN are supposed to be bound by a confidentiality agreement and are not supposed to tell the public they make parts for FN. So either FN's Vendor's don't care (or don't realize) about a legal agreement they signed onto (perfectly possible with the smaller shops), or the guys you are buying your parts from don't know and are just saying the parts are FN because that helps them sell the parts.
Remember though FN sells no AR-15s so there are no 'FN' fire control parts that should be used in AR-15s, same with bolt carriers. FN barrels should be so marked, should be 'pre ban style', 20" long, A2 profile (narrow under the handguards), and chrome lined. However since FN doesn't sell to the public that means these barrels were either stolen (from the company by employees, from the armory by soldiers, or from UPS/FedEx by their employees) or they are factory rejects that were sold as scrap.
The question is are you a betting man?