Clay, if I can make a technical note, that is *not* founded with a citation but just personal knowledge and opinion. . . .
My opinion would be you should never see the face of the receiver machined to accommodate the barrel. I do not believe this was a German practice. I haven’t been able to find detailed armorer instructions in regards to this service, but haven’t really looked either. Studying these would give us an excellent insight as to what was to be seen for the time period. Of course then, there are the rules, and then, there are the rules.
My opinion would be you should never see the face of the receiver machined to accommodate the barrel. I do not believe this was a German practice. I haven’t been able to find detailed armorer instructions in regards to this service, but haven’t really looked either. Studying these would give us an excellent insight as to what was to be seen for the time period. Of course then, there are the rules, and then, there are the rules.