i want to thank liev schreiber, i want to thank amy schumer. i want to apologize to matt damon.night miley cyrus and marlon wayans will be here. thank you for watching. "nightline" is next. good night! >>> tonight on "nightline," ak-47, sniper rifles, they're some of the most powerful weapons in america. and yet, we got our hands on them in the time it would take to get a pizza delivery. tonight, we're undercover. >>> and a medical mystery, waking up speaking swedish with no memory of your past, and suddenly taking on a foreign accent. tonight, what happens when your life seems lost in translation. >>> and what killed cory? why did glee actor cory >>> from new york city, this is "nightline" with dan abrams. >>> good evening, thank you for joining us, for many of us, owning a weapon is a constitutional right and one that many of us exercise proudly. but most law abiding gun owners may not think much about the ak-47s or the powerful sniper rifles, unless they're in the military. or they're criminals. so just how easy is it to get weapons? we found out. >> reporter: the u.s. is the