However several of the 'renewals' have included clauses without a grandfathering, or ones that allow the "attorney general' (read ATF) to declare firearms without the variously described features as also "assault weapons" at their discretion.
Then there was issues like in California where certain guns were declared allowed as long as they were registered before a specific date. Failure to register them was a felony, but if you registered them they would be grandfathered in.
Then later they said "oops",they are illegal and rounded them up from those who had registered them as required by law.
This happened with some SKS rifles.
Or grandfathered them in for the original owner, but made it a crime to transfer them to any regular person, effectively reducing the value of said firearms to nothing in said state.
This was the case in California, and could be the case in some national legislation as well.
Fortunately people in California could sell them to people out of state to offset the fact that the weapons become worthless in California, but if such a restriction was done at the national level your firearm becomes worth almost nothing with a tiny market of potential buyers. With the only option selling it to FFLs that will pay what they want and who can only sell it to law enforcement, which have so many and get government surplus that they won't pay even a fraction of the actual value.
You can't even leave your 'grandfathered' 'assault weapons' to family in state in California. Nor the 'grandfathered' 'high capacity' magazines. If you die or sell them to someone else they can never be possessed by a regular commoner within the state again, including your heirs.
In such a situation at the national level people that stock up for a ban would end up with firearms that can hardly be sold.
The other thing is the perception that changes when they are banned.
What can be normal is abnormal and scary 5-10 years later. I was surprised at how targeted firearms once viewed as just slightly worse by various people when they were legal become almost universally bad according to the majority once they had been banned long enough.
It is scary that once something is banned, you can force the population to support the ban as a new generation grows up with it having always been in place and afraid of the unknown.
Many of those that came of age during the AWB and knew nothing different actually believed it was accomplishing something.
And the population with less exposure becomes even more naive on the subject, plenty of people thought ARs in states like California were full auto m16s in 2003-2004.
It is the same situation you see with select fire weapons. You hear about how uncontrollable they are, how no regular person could safely use them, they are only good for spraying, essentially how such restrictions make us safer, and how they are fine with what they are prohibited from having, because obviously if it is prohibited there is a good reason for it. Such conclusions are heard even from gun people. Yet it is untrue, but since the population has the least experience with that which is most restricted or banned it is the scary unknown, where facts based on movies, games, and assumptions prevail.
If you prohibit the herd from owning something long enough they begin to defend the prohibition, having known nothing else and believing the fear of the unknown is justified and a change would be dramatic.
This also means even people that legally own such firearm or had them grandfathered go from normal to 'evil' in the eyes of society over time.
Once the majority of the herd has been unable to buy such things for a generation the people that have such things are seen as bad guys, nutjobs that think they are rambo and instantly are seen as the bad guy if they end up in court claiming self defense. The nutjob with a military rifle (or other "assault weapons" as the term has no real meaning, pistols with just a threaded barrel are an "assault weapon" in California), while normal people have other types of firearms.
