We live in a world of Big Data. Anything that has been bought, sold, texted, opined, etc, can be found and tracked, including that SCAR 17 that was bought with a credit card and shipped to an FFL, after which it was legally transferred to its owner. The 4473 is just one more little piece of the pie, but it’s not the only one. There’s already enough data out there to accomplish evil .gov intent. All it takes is the alignment of the oppressors passing some nasty piece of legislation, some alphabet agency getting free reign, and it’s done.
Sure, obviously private sales and buying things with cash or gold can be done, but that’s not the majority of sales, is it? What about that optic? That ammo? There is already enough data out there that almost everything can be tracked, if the effort is made. Heck. Look at what the ATF is able to do now, with tracking down people who have purchased certain items.
When it gets right down to it, if things get so bad, that they actually DO want to take that rifle, or other items, and the door gets kicked in at 3AM, saying stuff was lost in a “boating accident”, while cute and imaginative, won’t matter one bit when you’re face gets put in the dirt and you get dragged off in ziptie cuffs, with the orbiting aircraft and enforcement folks thinking it’s "just another day", not caring one bit about your protestations, and you wind up in some holding facility thinking that you’ll actually be allowed to “prove” your case. Along with a bunch of other people, in “Red Dawn” fashion.
Don’t get me wrong, I think using 4473’s as a tacit “registry”, or whatever one wants to call it, is wrong. But that ship has sailed. Big Data is already out there.
All we can do is ensure that our politicians and reps are the type of people who will stand against that.