Would he be creating a new machine gun? They said the gun build something like 50 years ago it just wasn't assembled. When the gun / kit was originally manufactured wouldn't the serial number have been recorded / registered? If so is he's not manufacturing a MG only putting it together.
"For civilian possession, all machineguns must have been manufactured and registered with the ATF prior to May 19, 1986 to be transferable between citizens. These machinegun prices have drastically escalated in value, especially items like registered sears and conversion-kits. Only a Class-II manufacturer (a FFL holder licensed to manufacture firearms or Type-07 license that has paid a Special Occupational Tax Stamp or SOT) could manufacture machineguns after that date, and they can only be sold to Government, law-enforcement, and military entities. Transfer can only be done to other SOT FFL-holders, and such FFL-holders must have a “demonstration letter” from a respective Government agency to receive such machineguns. Falsification and/or misuse of the “demo-letter” process can and has resulted in long jail sentences and felony convictions for violators."