Today I finally broke the CC weapon block I had, I decided to cut a strip of thick plasticard,and cut along the drawed line you see.
After that I sused some spare plasticard to form the weapon body.
Finally I glued the weapon to the arm and refined the cabling I already had pre placed:
If you are interested in the previous work here is a recompilation:
Arm without weapon and Big shoota completed
Initial work on the arm