Tell your FFL to read the CT general statute, specifically this section:
Sec. 53-202m. Circumstances when assault weapons exempt from limitations on transfers and registration requirements. Notwithstanding any provision of the general statutes, sections 53-202a to 53-202l, inclusive, shall not be construed to limit the transfer or require the registration of an assault weapon as defined in subdivision (3) or (4) of subsection (a) of section 53-202a, provided such firearm was legally manufactured prior to September 13, 1994.
That PWA lower was manufactured FAR before 9.13.94. Therefore, it is excempt from limitations on transfers. It can transfer to you with a collapsible stock all day long.
Who is your FFL and why does he not know this?