Jeff: Good points, and really nice guns in your pic. I love the A-5 and own four myself. In fact, I'd be happy to own the gun my buddy just bought -- I just don't think he will be. I thought he knew that not all 16s were "Sweet," but apparently not.
So if the gun is currently unaltered, does that process need to be a factory (or Art's) job, or can lots of gunsmiths do it? Also, based on your earlier post about "16-65" and "16-70," can I assume that all guns, even from 1932 (if that is really the year it was made), will be stamped like this, indicating the chamber length in millimeters?
I also agree that modifying the shells as discussed sounds like a real bad idea for several reasons, and a great way to obstruct a barrel with one shot and destroy it with the next. TT
