Berlin or Bust Wirbelwind WIP

I couldn't find any assembly instructions for the Berlin or Bust Wirbelwind, but after looking at several historic photos and other models, I was able to start the assembly.

Below are WIP photos of the gun assembly.  Hopefully, this may help some other modelers working on this same project.  

Comments are welcome, especially if you see something incorrect. 

The sculpt and casting is very good, but assembly is challenging with a multi-part, multi-glue point step as shown below.