[cyberia]

I'm thinking it came up on the sloop to the left at such an angle it tipped, but rolled so quick that the right hand top of the turret hit the ground and held it in place until underside came all the way up and it rested on its roof.

There is also the slim chance the gun was elevated and helped hold it in place until it was wrong side up.

Either way, if the crew got out it was not through the commanders hatch.