I am not the one to ask.
Jim Keenan, Old Fuff, rc model, mnrivrat, for starters, have more knowledge in their little fingers that I will ever know.
May I suggest a PM to Staff, and see if it would be best to either post a new thread in "Firearm Research", posting the question and linking to this thread, or moving this one over there.
Thank you "dusting off" some guns and sharing the pictures! *smile*