Thank you for the information. Very interesting to say the least.
Yale either went to the trouble of making separate firing pins w/bushings in that Win21 project or perhaps made smaller integral pins and bushed the breech face. It's been a while now & my recollection is failing me. You'd probably enjoy talking with him. Very talented gunsmith & builder.
I don't recall what all else he altered but I remember him talking about adding a cross bolt lockup to the system as the single underbolt was not enough to retain the action shut all the time.
Don't know if that modification actually came to be or not.

He's a working, advertising gunsmith,,no secret basement type.
Good machinest.

He was for several years in Yellow Jacket, Colorado. That's when I talked to him.

He's since moved his business:
J. David Yale
Delta, CO
970-874-1088

Just goes by 'David'.