There seems to be a lot of fear surrounding obeying the law.
You are a law-abiding citizen, and theoretically the law exists to offer you protection.
If you have a lawfully owned stripped lower, and the transfer is documented in an FFL's bound book, purchased at ANY point in the last 20 years, the seven day window provided by law to "register" it via FA-10 may well be your last opportunity to legally register it in MA.
Think about that.
Never mind what the AG says--what she says keeps changing--the LAW states that you have seven days.
IF the State goes the route of confiscation, and they might--well hey, everybody is in the same boat, and (as law-abiding citizens) we ALL have tough choices to make.
IF confiscation happens, you have options and choices. You can move it out of State, sell it, whatever--you can use whatever legal options are open to you.
IF you must surrender it, strip out all the parts, sell them to a friend in a free state and surrender the lower.
At that point you are out $100, but on the upside, there are no question marks beside your name when you go to re-up your LTC. That "no question marks" to me is worth $100, easy. YMMV.
But here is the upside of registering your build. If the AG's edict holds, but the State does NOT go the route of confiscation, you own a lawfully registered rifle.
IF the State tries to prosecute you for following the law AS IT IS WRITTEN--then I assume you have an actionable lawsuit against the Commonwealth of MA, and the law as it is written is on your side.
I understand that it is a little scary to register a lawfully-owned build (repeat: build, not lower) right now--but the letter of the law is on your side.
In the end that may not matter--but I'd say you should act like a law-abiding citizen in the meantime, because you ARE a law-abiding citizen, right?
That is how I see it.
ETA: See you at the rally--right? Is there ANY reason you are reading this thread but NOT attending the rally?