My gut feeling is that the demilling process is different now than it was for those magwells that you see being spliced to 80% lowers. The more recent demills you see are crushed into pieces or cut through the magwell basically making them unusable. Also, the ones people are picking up on GB were likely demilled by the Government; therefore, there is likely a record of that weapon officially being destroyed so the magwell is no more than a piece of scrap. If the weapon was originally manufactured in the US but demilled in some other country, there would be no record of that weapon officially being destroyed in this country possibly making it subject to the "once a machine gun, always a machine gun rule". Don't know if I would want to take the risk. Just my two bits.