This is not a view you get very often. It’s the F-35A’s GAU-22/A 25mm internal cannon opened up for the world to see its mechanical firing process, including the barrels hydraulically spinning up, the low-observable gun door and the vent door popping open. And of course lots of smoke and flames.
Source: Here’s A Rare Glimpse Of The F-35A’s Internal 25mm Cannon Firing