Hi, Ron,
Unless BATF changed its opinion, you were right the first time. They consider (or did consider) the barrel and receiver (not the grip piece) to be the firearm, for the reason you gave, that it can fire by itself. I know they ran into problems because the receiver does not normally have the full serial number but I don't know if they ever changed their position.
This is actually consistent with German nomenclature, where the bottom is called the grip piece, not the receiver.
Ruger asked to put the serial number on the receiver instead of the grip frame because the frame is too thin to take a number stamp without bending. ATF agreed, using the Luger as a precedent, even though they are different guns and the Ruger cannot be fired without the grip piece.
BTW, I have fired the Luger "top" by itself. Odd feel, but no damage done to me or the gun. The gun does not unlock, of course, since unlocking is done by the grip frame.
Jim
|