I don't know about this, aside from furniture/forgings, there's a lot of things specific to a ruger AR that is seen only on their rifles.I highly doubt that any of their AR parts are in house made. All sourced out to enable them to keeping their bread and butter firearms on a steady roll. Ruger has kept their shit together quite well unlike many other arms makers.
Just a short list
FSB is unique
Delta ring assembly is unique
BCG is fully compatible with standard BCG's, but is not cut exactly the same