To add to Mobhack, I have once witnessed even "Gun destroyed" message and the crew survived bar one casaulty. So yes, it is possible, but with good ol' suppression fire you won't make a mistake
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This post, as well as being an ambassador of death for the enemies of humanity, has a main message of peace and friendship.
It happens, but not very often. The people around the gun are much more vulnerable then the physical gun itself. Things like shrapnel, richochets, and small calibre projectiles aren't likely to do much damage if any at all to the metal of a gun but they will shred flesh. So usually crew attrition will knock out a gun.