There is a lot of information on how to do this – what’s interesting about this project is that with a Brown & Sharpe Omniversal Milling Machine, you can take the vertical head, tip it 90 degrees and you are able to drill the hole for the spring and detent for the extractor, which eliminates ever having to change your fixtures. It cuts the time in half, and no fancy fixtures to hold the bolt are needed. I have yet to figure out how many axis this milling machine actually has!  See Equipment link for more info on B&S Milling Machine.