> This particular F-35 has an externally mounted gatling gun that fires a 25mm armor piercing high explosive round. Sometime during the training, the gun discha

> This particular F-35 has an externally mounted gatling gun that fires a 25mm armor piercing high explosive round. Sometime during the training, the gun discharged and the round exploded, damaging the underside of the jet. There's probably redundant software to ensure that the gun never shoots the jet so I speculate this was a mechanical failure.