Compliance with California's required registration of "assault weapons", in the 1990s, was estimated at about ten percent. The official assessment by the CA Dept of Justice was that the registration effort had been a failure.

You might get a few. Very quickly, cops would refuse to go door to door (being fired from your job is better than being dead). Maybe you could get the military to do it.

There's a paper on this somewhere (I'll see if I can dig it up) that estimates the lifetime of firearms in the US at about 300 years, if we stopped selling them today and banned their transfer. I forget what the "confiscation" estimate was -- I don't think it changed much.

Hacker News relevance? Legislation doesn't solve a damned thing. Remember the crypto wars of the 90s? Imagine taking crypto away from people now.

[edit: not half-life, but lifetime]