A-20 and A-22 defensive gun firing arcs

[elbmc1969]

Yeah, you can see the notch that latches the arm at the 90 degree angle. Makes sense once you see it.

Where did you find this?

 

[MiTasol]

Yeah, you can see the notch that latches the arm at the 90 degree angle. Makes sense once you see it.

Where did you find this?

This is one of the diagrams in the below document. Your local library may well have access to JSTOR so you could access the full file there though there is no other mention of this gun mount. Likewise many schools have access.
Essentially the article covers most of the various means of illustrating aircraft and parts for production purposes. Surprisingly it does not include Schematics (which show how a system works). Copyright prevents me showing more. I expect that the whole article can also be purchased from SAE. Tharratt also wrote a manual on this subject that I have been chasing for eons.