Just listened to an Intelligence Squared debate on whether the 2nd Amendment has outlived its usefulness. Not a very useful or informative debate in my opinion.
The odd thing about the US is that guns are linked in the popular imagination with civic freedom and self-defence. In the early days they probably really did think that armed private citizens would be a protection against tyranny that arises from within your own country. But now your military and police forces are so powerful that it's pretty silly to think that private citizens owning guns would in some sense uphold, increase or guarantee better civic freedoms and freedom from tyranny from your own government.
So what's happened is that the focus has shifted to self-defence, which I don't think the drafters of the 2nd Amendment were really thinking of that much at all. From a European perspective the idea that guns are primarily for self-defence is really hard to get behind. We think that they are for hunting and target practice. We don't think that if someone threatens you, you should have the right to shoot them.
in Sweden or Finland you can get a gun if you want to. It's just that we think if you really need one because you hunt or go out in the wilderness or shooting is your hobby, then you should also be responsible with guns and shoulder the responsibility that comes with owning one. It's not like a pepper spray or a taser that you carry around so as to feel more secure that you can take a lot of people out in a fight. That would be seen as pretty cowardly I think.
Secondly, I think it's okay that police officers and the like can shoot people in the line of duty in certain circumstances. What justifies this is that their job requires them to put their life on the line to protect those of others. It's not for "self-defence" or to ensure that they come to no harm. They have to put the lives of others before their own, and as long as they do that, I'm pretty comfortable with the idea that they also wield firearms.
As to your 3 stage gun control experiment, I highly doubt that it would work. This is because it's not really about what is "more safe", as I understand it. People who passionately oppose gun control see it as a question of freedom and civil liberties. It's only a secondary argument when they say that you are also more safe when loads of people have guns. For this reason providing raw data that suggests tighter gun control means less violence would not really convince people that it's better. What they are opposed to is the curtailment of their freedoms.
Another problem is that if there are a lot of differences in gun laws between the states. policing state borders would become a problem. Right now you can move pretty freely, but in order for what you suggest to work reliably, you should essentially put up security checkpoints like we now have at airports through which you could then move between the different states. I don't think people would appreciate that very much, and it would be very expensive to organise and keep running.
I'm not opposed to the right to bear arms in the US. I think it's good that we have different countries with different laws. All I'm saying is that when I listen to debates about gun control or talk to people who are for the right to bear arms, what always strikes me most of all is this link you've forged between guns and freedom and guns and self-defence. The major difference in attitude between where I live and the States is, I would argue, that we don't think guns are for self-defence at all. They can be useful and good things, but we don't have this idea that you should be able to rapidly kill a number of people from a distance and that this makes you more free as an individual or a citizen.