I had read that the data was quite shoddy, based upon questions like "how many times have you defended yourself with a gun in the last 10 years," and that a lot of data on crime-prevention statistics comes from decades ago, when crime levels were naturally higher.

Found that in an op-ed somewhere after the Aurora shooting.

The 2nd amendment wasn't for hunting or home defense. It was the ultimate check on government authority. And considering we live in a world where the government kills US citizens with predator drones I think its become more important then ever before.

The second amendment is for exactly what it says its for: building a good militia, which was essential at the time when populations were lower and when it would've taken two days of marching to get troops from, for instance, Washington DC to the Chesapeake Bay. A well-regulated militia (note that the words "well-regulated are in the damn amendment! Not "everyone needs to be able to buy as many guns as they can no-questions-asked," but "well-regulated.") was indeed necessary for national security in that day and age, and stopped being at all necessary by the end of the troubles in the Old West.

Realistically, the entire amendment no longer has a damn thing to do with our modern society, at least if we're actually supposed to read the constitution literally. The current gun-rights interpretation, is, dare i say it, a liberal reading of the constitution

Actually, my data came from the Brady Foundation - America's premier anti-gun group. Their Brady Score directly correlates with murders in America. That is, the more the Brady foundation approves of regulations, the more murders occur.

That is a good point actually.   Pretty much anybody could make their own Assault Rifle in their garage with some fairly common tools.

things never are truly intended for what they become, when first set up, i mean look at marxism. Karl Marx wouldn't of liked the way Stalin ran things, communism wasn't spose to be authoritarian or repressive. Just like the 2nd Amendment, sposed to be liberal but people took advantage of it and let many shootings happen

gun laws don't work in Chicago because you can go to the next state or even city and buy your weapons legally to do your dirt, just like the mexican Cartels come to the US to buy their weapons.

That's the problem with written and protected constitution's like the USA's, they don't adapt well to change because they can't. America is 236 now, it needs a constitution that's relevant to modern society with some major amendments thrown it. society was very different during george washington's life as to barack obama's. That constitution starting to show it age

... and how many gun crimes are committed with legally purchased guns?

I haven't seen the statistics myself but I would expect that it would be (roughly) 0.

Edit: On the Mexican cartels, outside of guns provided by the federal government, the cartels do not buy their guns legally in the United States

yeah if that applied nationwide, it would probably drop to 50 murders or less a year