One thing you failed to mention, AR-15s are incredibly easy to turn into automatic. I know, i've seen it done and used one. It takes all of a few minutes to change it from legal to illegal destroy that spare fridge and mod it back to legal again. I'm not sure how easy it is for other guns like this, but I was pretty amazed to see this in person. As a small kid at the time, it was the coolest thing ever. As an adult, it's the most terrifying thing ever.