That's not correct. Bushmaster and others such as Olympic Arms made many auto pistols on the AR platform. I used to own one. They were not SBRs and they did not require a tax stamp. As I recall, the barrel was about 9 inches and did not have a stock. It was cool, but really more of a novelty and kind of useless...just a bullet hose. However, I never heard of one being used in a crime. A few years back Bushmaster was still selling them for around $1000 to $1100.