Personally, I think the MAC tests are kind of silly.
The Scorpion made it through the 'Elements' test just fine (already a pretty good example of its durability, imo), then made it through the water part of the 'Gauntlet' just fine. Had a jam on the sand, and then was able to fire again once it was cleared and cycled correctly. I wouldn't exactly describe that as "it did really poorly."
As for the rest, I got bored. I don't plan on ever burying my Scorpion in dirt. But especially not after already having subjected it to the rest of the above without at least a minimal cleaning.
I still have no reservations about the durability of my Scorpion, under realistic conditions, whatsoever.