You can see the ball turret guns pointed straight down, which means the gunner has probably peaced-out, as that's the position it needs to be in for the hatch into the plane to open.
I've seen that footage in a ton of ww2 gun cam videos, so I'd wager it's probably authentic to answer an earlier question.
This YT channel has some good videos on L/W 30mm and 20mm guns effectiveness.