The chlorine bleach as well as the chlorine and vinegar options will help BUT in my experience, they won't totally solve the problem (Don't know why as chlorine gas should kill everything.)
I found that you needed lots of sunshine and coffee to finish the job.
ALSO, IMPORTANTLY, the Chlorine can and will bleach out the fabric colors of the cloth inside cases. I wouldn't use it to get rid of the musty smell on guns. Lemon oil or Lemon polish, may be a better bet for that - along with lots of sunshine.
