Well one question!! Is this really that much different from American guns. The vast majority of older double makers sent out their guns bored F/F unless otherwise ordered. German specs I have seen called for a constriction of approx 1MM for full choke.
Most older US guns bored full seem to have approx .040" constriction.
Do the Math, Note 1mm =.03937"
Do you "REALLY" see a great difference??

Miller/TN
I Didn't Say Everything I Said, Yogi Berra