I have installed FSX Boeing PW-9 and all is working including the canon almost. I have the tracer showing and the shells ejecting, but no sound. The sound file 20can.wav is there and I have pretty much put it in practically every folder. I have also added what I think is needed to the sound.cfg file as follows:
I put this at the end of the sound.cfg in the sound folder in the airplane folder.
I am using FSX Steam Edition. What else do I need to do to get the sound? All other sounds are working.