He’ll start twitching again when he get’s *out* of the war zone. At least for a while.
I don’t think that having spent much of my life in parts of urban America where small-arms fire is not uncommon would even make much difference in how I’d react.
There is a significant difference between hearing sparodic 9mm fire, and freakin’ artillery.
Another benefit of experience is being able to tell the difference between incoming and outgoing fire. Outgoing is actually somewhat cheering (unless you’re trying to sleep), it means that someone is catching Hell somewhere else and serves ‘em right.
Incoming means it’s your turn in the barrel, which isn’t nearly as much fun.