The gun had the date 1974 stamped on it and appeared to be “very heavily used,” records show.
The weapon also was sawed off and had a “tactical sling mounted to it.”
Aebischer told Blackwell investigators he traded Harvey a pistol and $500 in cash for the AK-47.
Aebischer and Harvey were arrested Friday.
Both men were released on $5,000 bond Monday after appearing in federal court in Oklahoma City.
The two are charged with one count of possessing an unregistered machine gun, court records show. If convicted, the two men face up to 10 years in federal prison and a $250,000 fine.