Previously I have made some videos on milling out 80% polymer lower receivers. Using a drill press, I recently milled another Hybrid80 lower according to their new instructions, which relies heavily on the end mill. I think overall it is a easier process than the previous instructions put out by Tennessee Arms Company and Hybrid80. A hour or two on the drill press and you are well on your way to making your own AR-15 / M-4 rifle or pistol.
You can find the Instructions Here.