Now: Turn in your guns, please
Later: Turn in your guns.
Even Later: Turn in your guns, Now!
Still Later: Any private citizen caught with a firearm on their person will be.....
You get the picture.
No they always toss in a licensing system or permit system before the last part, to try and get a better idea of who still has what needs to be taken later.
And severe punishments for anyone that has a gun and does not get that license. Then wait several years for most people to obtain the license. They can then gradually require the turning in of some, a condition which allows the keeping of other less capable arms.
Refusal to turn in those specific types would of course then be a felony. Which means no guns at all for those who don't turn in what is outlawed.
That makes it easier to take them. If most were simply declared illegal then they know many will not turn them in. If people are given a legal method to still continue to own them, but must register first or obtain a permit, they can get a roster of owners who sign up for the permit/license. They then know where to go for specific weapons after future legislation.
That has been the method around the world. It is also why most private held NFA items were not registered when that legal option existed. The lack of many registering is probably also why the NFA never went to the next step, and the limited number has remained legal. They estimate only a tiny fraction of all previously legally sold and possessed NFA items were registered once the NFA was passed.
There was no requirement for bound books, 4473s or other records to go through though, only manufacturer sales numbers. So they know they were sold, but not to who. So they know those registered after the passage of the law was a tiny percentage of what was sold and therefor possessed before the law.
It is easier to control guns by keeping some legal, outlawing most, and adding tons of growing red tape to the few kept legal (like shotguns.) Far fewer people will physically fight for a gradual loss of thier guns, but a sudden loss they will.
From a government perspective, that means stability, less resistance, yet still a removal of those arms which are seen as posing a threat to absolute power. While a complete ban is counter effective, creating instability, resistance, and less compliance.
Even the UK and Australia knew this, and hence do not have a complete ban.
A complete ban result in many the government does not know about being used, built, sold, imported and exported. Severe restrictions but still some legal means they can limit, reduce, track and control those which are legally possessed.
Making the only market the black market leads to complete loss of control over guns, the type of guns made or possessed (select fire, armor defeating etc), the number of guns, etc
While severely controlling but allowing a limited market does not create such a massive black market because those gun owners are less prone to break the law, the sellers and dealers more likely to comply with the law, and compliance with methods of tracking, registration, and other things important to control are complied with.
