He started with a Remington receiver and threaded and chambered a barrel, made a stock from a blank, and finished it into a 223.
http://www.diynetwork.com/diy/shows_dtrs/episode/0,2499,DIY_21538_38200,00.html
http://www.diynetwork.com/diy/shows_dtrs/episode/0,2499,DIY_21538_38200,00.html