That doesn’t answer the OP’s question but I can certainly see how your first sentence is operative.To get back to the point, the most common approach seems to be delay. They’ll “grandfather” you in, but your kids will be out of luck. When you croak it will be, “Turn them in, or we will come and get them.” They’re likely hoping by that time they will have created enough social stigma surrounding the rifles in question that the next generation will be willing to go along with it. The kids didn’t pay for the rifles, so why should they care? I think that’s the “mentality.” (Term used loosely.)
There are two related goals with that approach, particularly at the National rather than state level.
1) By grand fathering and allowing you to retain the banned weapon they do not have to get into justifying the taking of your property without compensation by proving it is a public safety concern, or deal with litigation to that effect.
2) Not allowing those grandfathered weapons to be sold or even transferred to anyone else is a more serious infringement. Yes, you can still possess it and use it, but that property immediately loses all cash value as it can no longer be sold or transferred, including to your heirs upon your death.
Since it cannot be transferred, even to your heirs, the banned weapons must eventually be destroyed after you die, so the numbers of weapons still in existence starts dropping immediately.
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In both cases since we are Americans who on average lack much of a sense of history, and generally suck at looking at where things are eventually going to go, these kinds of bans get more support and get less resistance as no one is losing anything *today*. The average American also doesn’t connect the dots to see how the kind of precedent set in a gun ban and watering down 2A rights can and will spread to other items and other rights.
In fact, at present, given that gun owners are a minority (about 40% of households have guns and about 32% of Americans actually own a gun) we currently rely on at least a third of the non gun owning voters out there opposing gun bans based on the recognition that it could be their rights next.
A big part of keeping those voters on our side is also presenting as normal people who just happen to own and shoot guns, as opposed to presenting as inconsiderate, and or ignorant, and or irresponsible people who should not own guns.