Observation

[DRG]

Killing the crew destroys the gun. That is SOP for the game. When the crew dies or is dispersed, the gun is destroyed as only that crew can operate that guns....no crew, no gun. It's possible there was only one crew left for that gun but the only way to know that is to post the save game

[Imp]

Limitations of the game system, crewed weapons are vulnerable as considered grouped round the weapon rather than dispersed as a squad could be.
Units can only have one state so as most of their time is spent stationary manning the weapon thats whats modeled.
They are very vulnerable therefore when moving or transported.
Not unfeasable as again restricted only that crew can man that gun.
If fired on by a sniper its fair to assume the crew would disperse to save themselves at least till the threat is neutralised, in game terms its out of action thats a kill.

[Warnevada]

This was a fully crewed gun which was moving up to the front. Hadn't been in action prior.

I can understand how destroying the crew would in effect destroy the gun. And I can accept that repeated small arms fire will do that. What is incredible to me is that a single shot could do it.