This 20 gauge Merkel must be different from most Merkels I have measured. Most I have measured are undersized rather than oversized.
Eightbore, I wonder if things changed from pre-WWII to post-war guns. I've observed the same thing you have on the E. German Merkels: often underbored, sometimes quite significantly so. I just acquired a pre-war (1936) Sauer 20, and it goes the other way: marked 19 on the flats, and the bore gauge confirms it's overbored from the standard 20 by about .012. And I've recently seen photos of a couple pre-war German 16's, one of them on this BB, that were 16/1 guns. Maybe Raimey would know how common overboring was in those older German guns.
