> You don’t actually need a VIN on a car, you just won’t be able to register and drive a VINless car on public roads.

Somehow I doubt that many 2nd amendment supporters would be okay with "You don't need a registration number on your gun, it'll just be illegal to carry/use it anywhere except private property"

Some would, some wouldn’t. There are some who only care about home defense or sport shooting on private land. Open carry and CCW folks would be quite upset, yes.

The biggest problem with this (for the first group) would be conveyance from buyer to seller or to/from a range or hunting grounds.