Let me make sure I've got what you're saying correct:
Banning or heavily regulating guns that people already legally own, guns that have been widely considered a constitutional right for >75 years, is not the same as "taking your guns", is that correct? Would it be fair to say that they only thing you would consider to be "taking your guns" would be house-to-house confiscation of all firearms in private hands?
In re: bump stocks - it turns out that a lot of people that purchased them (and forced reset triggers, which are a similar concept) got letters from the ATF telling them that they had to turn them in or destroy them. Because, see, the ATF could just force the companies that sold them to disclose customer records, which means yeah, they could come to your door and take it. Unless you paid cash at a gun store, there's an electronic trail, and the ATF followed it for a whoooooooole lot of people. Continuing to keep one that you purchased legally at the time? That's a felony, because the ATF has re-classified them as machine guns, which means you can't own one since they were produced post-ban, and there's no way to make it legal. (Currently, there's an appeals court that has ruled the ban illegal, but we'll have to see how that plays out.)