There is a law called the National Firearms Act that was implemented in 1934 that "regulates" (read that mega-taxed) machine guns. It was brought into law basically as a response to the St. Valentine's Day Massacre where 7 guys were executed by 4 guys with machine guns. So not being a gun guy, I would like to know what the difference is between the original definition of a machine gun which means any weapon that can be fired more than once with a single trigger pull, at least the way I understand it. This to me begs the question why an AR-15 or equivalent isn't a machine gun and why isn't it heavily regulated the way machine guns are? I'm not at all a gun control advocate, but if we already have a law that's been on the books for 90 years that already taxes the crap out of machine guns, wouldn't that same tax and regulation extend to modern semi-automatic weapons?