Just returned from a visit to Vienna where I was able to visit the Heeresgeschichtliches Museum. A beautiful location with lots of very interesting artillery pieces. Although very nicely arranged I found that the lighting was very low and as a result it was "all in the dark" with spotlighting making it difficult to photograph. (Photographs, on this site of earlier visits show a better light condition). Unfortunately I had the same experience in several other musea where low lighting and reflecting glass panels makes it very difficult to photograph.
I tried to capture the total length of the pieces but due to space limitation and standing point I had to zoom out and use a stacking focus approach causing all kind of distortions where dimensions and alingnments go wrong.
The very limited information on the use of the 38cm on the Western front. ( source unkown )