How long would the Nazis have kept it up if every Jew they came for had met them with a gun in his hand?
When you purchase a gun from a gun store, you fill out a form 4473, for the purposes of a background check. The ATF has a record of gun transfers, but not a list of who currently owns a gun. If they recover a gun from a crime scene, then can go through the records to see who was the last owner.
The kink in this system is that private sales of guns is legal in most states as well. No background check, no record keeping required, just a good faith effort to ensure that the person you're selling it to can legally own a firearm.
So if the police come knocking on your door and ask for your guns, you can simply say "I sold it 2 years ago, but unfortunately I didn't keep any information on the new owner." The police would then need to have probable cause to search your residence for the weapon (which they very well could get depending on the evidence they have).
Collecting all the guns in the US won't be an easy task.
"Collecting all the guns in the US won't be an easy task."
Definitely not, but I would think that to be something an oppressive government would try to do. In that case, the police might not ask nicely.
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]