I see the words for the definition of a receiver, but I don’t know how that actually fits into the wall? So you can still work in an 80% receiver but as long as you put a number on it it’s OK? Or does that mean you have to file some ATF paperwork?
IMO, no. You apply a number and call it good. One issue is . IF and WHEN one were to have a LE run someone's serial number. It only comes back, or use to, if it was stolen. Then again w/out a search warrant GFL. Oh right is still CO.