Doesn't the title answer your question?
NM Box wired with MC cable?
First, is the box listed for MC?
Second, ok, you brought a ground into the box. What about the outer shield? where is it connected? Do you have a grounding bushing? (being that least one end is not connected to a metallic part). A metallic connector should be connected to a metallic box (least on one side).
Personally when I install a metallic connector into a non metallic box (if I really have to do it), I install a grounding bushing.
Arlington makes a great box for drop ceillings in the support of heavier loads. Can't see why we can't use this box in our commerical jobs. Inspector shot it down and called the state inspector and he backed him up saying it was illegal. I was looking at 314.3 and I believe that article supports my view. Any thoughts?
Thanks