Tom, the tiny screws that hold the firing pins in are an 8-32 thread and are a little under 3/8" long. They are set an a compound angle in the breech ball. I had to drill one out, and used the hole from the other to find the angles. Luckily I have a bench mounted drill press that has a rotating head to do this. If the screws in yours are damaged you need to use a center drill to make sure that you drill the hole in line with the existing one.
If you need these "set screws and hammer drop me an email. My contact information is also after my name or in the envelope.