These regulations go far beyond the question of "80% lowers" or "ghost guns".
So far, nobody here has discussed these consequences of the proposed regulations:
1) All upper receivers and bolt carrier groups used in AR-15s become subject to control as frames/receivers, and therefore can only be purchased through FFLs. That means no more purchasing "complete uppers" without filling out a 4473. It also means filling out a 4473 for every spare BCG you buy. And for every spare upper receiver you purchase for that future "build".
Every AR sold through a dealer would have at least three serial numbers. Those two extra serial numbers are sure to take a bite out of crime.
2) All firearm "parts kits", like those sold by Palmetto State and many others, that can be readily assembled by end users into functional firearms with the addition of only a serialized lower receiver would only be available for purchase through FFLs after completing a 4473. These 4473s would be IN ADDITION to those currently required for the lower receiver.
Undescribed: when do the parts you buy from a variety of manufacturers become a "parts kit" that can only be bought through an FFL?
3) All revolver cylinders will be subject to control as frames/receivers, and therefore can only be purchased through FFLs. No more converting the caliber of your favorite revolver without filling out a 4473, if it involves installation of a new cylinder.
Of course, buying a new cylinder is a major source of "crime guns", right?
4) The slides of virtually every semi-automatic handgun currently made would also be subject to control as a frame/receiver. A new Glock 17 slide would have to be serialized. If you want to buy a second slide for your favorite Glock and set it up for a red-dot mount, then this second slide would also require a serial number, manufacturer marking and could only be purchased through an FFL after filling out a 4473.
Spare slides, coming to a crime scene near you!
5) Suppressors often use components that adapt that suppressor to various firearms. One mounting device might adapt a particular suppressor for use on a Browning-style handgun, and a different mounting device for, say, mounting on a PCC with a fixed barrel. Under these proposed regulations, both mounting devices must be serialized, marked with manufacturer information, and could only be purchased through a dealer, after filling out a 4473.
One unanswered question: would each of these mounts require a separate tax stamp?
6) All federally licensed dealers/gunsmiths/pawn shops/etc. would be authorized to refuse to accept any AR upper receiver/AR BCG/revolver cylinder/autopistol slide until these components are marked with serial number, manufacturer information, etc. So, what are currently considered to be "parts", or "pieces of metal", but definitely not "firearms", would have to be serialized and marked as firearms when they are pawned, consigned for sale by an FFL, or go to the gunsmith.
How will any of these proposed changes, especially the additional background checks associated with every additional 4473, reduce crime?