"Technically", it sure seems like it. At some point in the build process it becomes a "firearm" and possession without a SN would be illegal. MFG's are allowed a certain amount of time to serialize a newly mfg'ed firearm, but HB2005 doesn't appear to have any provision for that. So far as I know.I've been pondering the path for future PMFs... Does it kill real PMFs? Will it be possible to serialize at a reasonable point in the mfg. process?
When I say real PMF, I mean from a block of alloy.
It's easily argued too that even if you do take it in to be serialized after completion, you may be self incriminating by documenting you were in possession of an illegal PMF.
Will the powers that be look the other way for newly created PMF's so long as they are serialized within a "reasonable" amount of time and demonstrating diligent effort to satisfy the law? That's guesswork. It certainly seems reasonable they should, but there isn't anything that I'm aware of that a person could rely on for a legal defense if they chose to jam a person up for it.