The design of the chamber in picture "B" is definitely wrong and has already been contradicted in an article from the museum in the early 20th century. They´ve done a new 3D-computer-analysis of the barrel a few years ago, but unfortunatelly the results have not been published until now.
http://objektkatalog.gnm.de/objekt/W2034
Maybe it´s the best idea to pick up the measurements given by the museum. They can be found in one of the latest publications containing the oldest clearly datable handguns from Tannenberg, too - the PhD thesis of W. Tittmann (Bochum 2015).