I thought they took care of most of those problem but, I may have to stand corrected. I do remember seeing a video with a "fixed" AR that was buried in sand and even underwater that still operated, but maybe that was some custom demonstration video I saw and the military hasn't adopted.
Many people/companies have been working on piston ARs... this may be what you saw. They're basically the best of both worlds (in theory) with regard to an AK and an AR.
Here's one company...
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