That doesn't sound legal to me (IANAL)..
By MA law a frame/receiver is not a firearm.
I would assume that most (if not all), gunsmiths are FFLs (by federal law and state law).
The gunsmith takes posession of the frame and with that custom builds a functional firearm. Since the smith is an FFL, and is now in full posession of a completed firearm, can he legally transfer a firearm that is not on the EOPS list, back to the original owner? I'm guessing that he can't.
Except that he isn't transferring a firearm, which implies a change in ownership; hes simply returning it to it's original owner. While that might not be legal for a Massachusetts licensed firearms dealer, it's perfectly legal for a gunsmith.
Which brings up another question...
At what point/stage of construction, does a frame become a firearm according to MA law?
When it's capable of discharging a shot or bullet. (MGL Chapter 140, Section 141)
And just in case someone suggests it... I kind'a doubt it would be legal for the smith to build the gun, then strip it down and send the parts/frame seperatly.
Doesn't seem to be any law prohibiting it, so I guess that means that it is.
Ken