The screws I sent to Flatlander .172 X40 when I made these screws I had 2 Ballard actions sitting on the lathe.  The lever & hammer screws are .227X40 trigger plate screws .135x42 all other screws for the Ballard .172 X 40. #8 screws are .164 Machinery's hand book has #8 screws .164 max and .158 mim. Taps the 6X40 STI Tap is the closes I could come to the .172 screws .227X40 nothing close the .135X42 good luck on that one I almost had both made it cost almost the same to have 12 made as to have 1 made. at this time all I have for the sight screws are one I made for Parts Unknow/ Red River .263 Head .250 shank Ken