Bob,
That really is a great question and another good reason to buy a set of Michael's books. Treat yourself, it's Christmas. If you a re not familiar with knurling on a lathe, there may be a video of the process on Youtube. In any case, you set up a lenghth of fair sized tubing (don't remember the size) and knurl it. A knurling tool has two wheels with opposing lines on two wheels. this is fed up and down the length of pipe until it appears to be 'checkered". Then they cut out a section and shaped and beat it over a mandrel or fixture to form the butplate. I am sure it took some final shaping. Michael noted that these would be color hardened and those that did not produce color satisfactorily would be blued. Michael acquired this information from former employee face to face and recordings of those conversations exist I believe.
