The sear and hammer pin holes in the frame. Do they take a 30 degree cut or a 60 degree cut. The picture in the Kuhnhausen book is confusing me. It looks like a total of 60 degrees.
From what I can can tell, you can pretty well pick what ever degree CS you want, with minimal depth. I think that the hole should be CS just for stress riser purposes. But someone with a more intelligent answer is likely to chime in.
60 degree countersink. The pins have heads that has to sit down below the surface of the frame so that they are clear of the thumb safety.