Originally Posted by onewheat
But an 80% aluminum lower has no serial number and can be sent through the postal service too. There are YouTube videos with guys making AR lowers out of aluminum in their garage too. If I was looking for illegal weapons - I'd want one that at least I knew was going to fire when I needed it - if you read about the guys making plastic lowers, they have lots of failures and their "successes" get them a couple hundred shots before they break or wear out. I get your point though - it is feasible to do so - just not very practical given the other better options out there.
Which is easier and more portable- buying a program and a printer, or learning to use a milling machine to close tolerances?