OK, I don't actually know much about the AR-15 specifically. I know a little about guns from table top RPGs (think D&D, but modern, so with guns), but I know a lot about knives. I got my first Swiss Army knife when I was a cub scout, around 8, and I have carried a pocket knife ever since, when legally allowed.
Different localities have different laws on knives, but at the federal level, there are some restrictions on "switchblades." Let's get something out of the way right now. Switchblades are stupid. Even if an attacker wanted to use a knife as a weapon (and knives are problematic weapons for many reasons), a switchblade has two intrinsic problems: 1) the mechanism is a failure point, and 2) the "k-chnk" noise nullifies the element of surprise. There are other problems to conventional switchblade designs, which can be addressed with alternative engineering, but basically, switchblades are stupid.
Just because switchblades are stupid, though, doesn't mean people won't want them. So, manufacturers have spent years finding ways to design knives that operate in ways that mimic switchblades without running afoul of switchblade laws. The result has included the "assisted open" design. Perhaps the most famous, at least among the knife crowd, is the "Kershaw leek," designed by Ken Onion (get it?). Why is this not a switchblade? Well, federal switchblade laws say that a knife is a switchblade if it has a button in the handle of the knife that triggers the mechanism releasing the blade. That isn't how the leek is designed. Instead, the blade itself has a blunt extension that sticks out past the other end when closed. See that little triangle thingy when the knife is closed? That's the blunt end of the blade. Press it in, and you are pressing the blade out. Once you press that out just enough, a spring takes over, and the blade shoots out. Like a switchblade. Functionally, exactly like a switchblade. Except that instead of the button being in the handle, you are just pressing a "flipper" on the blade itself so that the blade "flips" open.
Not a switchblade, except that from a user's perspective, it operates exactly like a switchblade. Assisted-opening mechanisms have been knife manufacturers' response to restrictions on switchblades, and anyone who wants a switchblade can get something that functions the exact same way but doesn't meet the technical definition.
The postscript here is Freddie Gray. You probably know that name. You know what the cops used as a reason to arrest him? An assisted-open knife. They called it a switchblade, even though it wasn't, under the legal definition. Gee, I wonder if there was some characteristic of Freddie Gray that made the cops unlikely to apply the law in a fair way to him... Gee, I wonder if that might have any additional relevance to any other discussion of the distinction between legal and illegal weapons...
So I promised a post on the AR-15. What does any of this have to do with the AR-15? Currently, gun control advocates are obsessed with banning either the AR-15 itself, or guns like it. Ban the AR-15 itself, and its competitors would obviously gain a lot of market share. Invest in whoever manufactures other assault rifles! If somebody banned that style of gun? Then watch how engineers find ways to build around the restrictions, just like knife manufacturers and assisted-opening mechanisms. Engineers are smarter than gun control advocates, and there's no such thing as a set of rules that can't be hacked.
And that's before we get into the black market issue, the Ruby Ridge issue, and all of the other topics I have been addressing recently.
And yes, I own a Kershaw leek. Just because they're stupid doesn't mean they aren't kinda cool. It's a glorified letter opener. I open letters with it. Or, rather, I open junk mail with it.