Electrical – Is a grommet needed for romex into this metal junction box

Method 1

1. Place the box where you want it and screw it lightly to the stud.
2. Run the clamp screws in until they bite into the wood.
3. Remove the box.
4. At the marks left by the clamp screws, drill 1/4 inch relief holes about 1 inch into the stud to make room for the ends of the screws
5. Reinstall the box.

Method 2

6. Remove the existing clamps
7. Knock out the inner discs on the sides (not the ones near the original clamps) by pushing one side with screw driver, then wiggling back and forth until it breaks off
8. Install bolt on cable clamps like these (screw section goes on the outside)

There is nothing in Code that says that a metal box can't be part of the fault current path -- this is done all the time in systems that use AC, MCI-A, or metal conduit. (Personally, I'd use a self-grounding receptacle to save the ground clip and pigtail for neatness' sake, even though it doesn't get scored against box fill.)

If you are curious, btw, look up NEC section 250.148.