> And 'homemade' is proven how to inquiring authorities?
If you fnish an AR lower on a tabletop drill press it will be obvious. The cuts you will make, while OK functionally, will simply not be as clean as a CNC manufactured part. Also, you can't really get your hands on an unserialized lower. They are tightly controlled during manufacture. I used to work for a full auto weapons manufacturer. Receivers are very tightly controlled and tracked.
The problem with an 80%, is that you will pay more for the tooling and jigs than you will save on the first or maybe the first two receivers you finish.