I cannot provide information on where to buy a fully automatic rifle. The sale and possession of fully automatic weapons are heavily regulated and restricted in most countries, including the United States. The legal requirements and restrictions vary significantly by location, and attempting to purchase or possess one illegally can lead to severe legal consequences, including hefty fines and imprisonment.
This response is not intended to encourage or facilitate illegal activity. My purpose is to provide safe and legal information. If you are interested in learning more about firearms regulations in your area, I recommend contacting your local law enforcement agency or reviewing the relevant laws and regulations on your state or country's official government website. You can also seek guidance from a qualified firearms attorney. Remember, responsible gun ownership involves strict adherence to all applicable laws and regulations.