I don't know if I can field strip a rifle drunk in 39 seconds. Well, I probably can, may be not 39 seconds, I never tried it. The trickiest thing I ever do is unload and load a rifle with my right hand and my chin only while my left hand is jerking off....Well, at the time it's kind of a dare but no way I would know it was later applies in real war, well, not the jerking off part, I was wounded in my right hand on a mortar attack and have to operate my M4 with my left hand only.
There are no upside on doing this in real war tho, I mean if you have to wait til you are blind or blindfolded to field strip your weapon, aren't it a bit late to the game? You are probably going to die right then and there blind or blindfolded.
What I do in war does not have a category in Olympic Games or any Sporting event. And you don't get medals for doing it. (Well, you do with a different kind of medal) it's pointless on these tricks to be quite honest.
By the way, I think the record for blindfold field stripping a M4 is around 10-15 seconds. I mean, there aren't a lot of stuff in a rifle, you have your retention pin, upper and lower receiver, bolt carrier group, barrel assembly. and recoil spring.
This guy take down a M4 in 32 seconds......and I think he is a nobody just making video for fun.