It alarms me how many people I have to explain this to, especially when visiting family in/from California or New York.
No, you cannot just run out and buy a “machine gun”. You cannot just legally purchase a full auto firearm of any kind here in the USA. They are restricted, as are short barreled shotguns. You have to jump through a fair amount of hoops to buy one, and then once you do, a full-auto rifle ain’t cheap. They usually cost five to ten times what their semi-auto versions run for. Tip to the non-gun literate.