The wire ran is 6/2
I just picked up that box because the holes for the plug on the box matched up with the 50A plug I was installing. I "assumed" it was meant for the plug... I couldn't really find anything else that looked like it would work I also couldn't find anything that was rated for 6/2 in a plastic box so I was kind forced to use metal.
as for the screws, I couldn't manage to get the screws drove in from a deeper position in the box even if I had drilled holes. there just wasn't enough room.
I figured I just haven't ran across the proper cover.
The piece I put on backwards to cover everything up was the only way I could figure to cover it, but it really doesn't give a decent finished look.
The information for working on 220 stuff is pretty scarce online and in the few books I've read.
for summary...
to get a nice finished project, get the deep 4" box install it, then the mud ring mounts to the box, the outlet mounts to the mud ring, and then the cover plate can be used (I actually have those cover plates already, just couldn't figure out how to mount it).
Also I need to make sure to get the 3/4 mud ring so that it mounts flush with the 5/8 sheetrock
I reckon I'll probably just rip it out and do it right, I'll feel better about it. I'll tackle one of em tonight, post up some pics to make sure that I did it correctly.