Designed in CAD for you.
I’ve teased some photos below of a large scale Bofors 40mm cannon I’ve been working on. It is now available at Shapeways as a kit in 1:16, 1:20, and 1:24 scales. (Please don’t wait around for offerings in 1:35 or 1:48, the model as designed won’t go that small).
The kit is currently only offered in “Frosted Detail” plastic, a multijet printed medium that produces fine detail, but which also causes these large models to be a bit of an investment– sorry about that! But please see my instructions for working with this plastic, it ain’t the same as your familiar model kit styrene!
The Bofors 40mm kit also has a complete instruction set, which can be downloaded and saved at any time.
The actual 1:16 version, assembled.
Instruction manual is available online.
Instructions include clear images for step-by-step assembly.
Matthews Model Marine 
But I need 1:50 or at least 1:48 double for a Museum model.
Let me know when you find one! It is a completely different weapon. Here’s the manual:
Here you go: https://www.shapeways.com/product/NH6Q3NR6E/twin-bofor-kit-1-48?li=search-results-3&optionId=59192603