Well, if we want to be really precise, (real) AK-47’s aren’t even machine guns, but assault rifles, correct? Though I think a lot of assault rifles and battle rifles got lumped into the “machine gun” catch-all under some federal laws...
From the NRA:
http://www.nraila.org/Issues/FireArmsGlossary/Default.aspx
ASSAULT RIFLE
By U.S. Army definition, a selective-fire rifle chambered for a cartridge of intermediate power. If applied to any semi-automatic firearm regardless of its cosmetic similarity to a true assault rifle, the term is incorrect.