not a problem
How could an SOT legally possess these item(s), if they were Classified / Defined as Unregistered NFA Items at the time they come into in his possession ? I have never read an exemption covering SOT's from possessing Unregistered NFA Items.
Demill requirements have changed over time, yes?
Ever see those demilled BAR receiver sections that were mill press sheared with the internals in place? The government must have been satisfied of those demills prior to selling them as scrap metal. If an SOT shopped for overlapping sections, would enough of those sections put together to "complete" a receiver be verboten?
I'm not an SOT nor do I play one on TV, just looking for the logic if any.