James,
There have been some interesting developments in the world of 80% complete AR lowers. The following are some companies that are producing beefed up AR-15 carbon fiber or polymer lowers that can be completed more easily than their older generation aluminum relatives:
Another innovation is a jig that allows a hand router to be used to mill out the control pocket of an AR-15 80% aluminum lower.
As many of your readers already know, the lower receiver is the part with a serial number that the BATF considers a “firearm.” However, an 80% lower is not considered a firearm by the BATF. As a result,[in most states] anyone who can legally own a firearm can purchase an 80% lower without going through an FFL, and unencumbered individuals are allowed to manufacture firearms for their personal use without paying any Federal taxes or completing any Federal paperwork. Check your state and local laws to be certain, in your locale.
Also, although I wouldn’t recommend it for OPSEC reasons, 80% lowers and parts kits are available through Amazon. Here is an example.
Merry Christmas! – R.L.H. from Ohio