According to Dutch state broadcaster NOS, an F-16 was hit by its own bullet(s) in a training exercise:
De F-16 die in januari aanzienlijke schade opliep tijdens een oefening boven Vlieland blijkt geraakt te zijn door zijn eigen munitie.
The F-16 that in January suffered considerable damage during a training exercise above Vlieland turns out to have been hit by its own ammunition.
They also added a picture of the damage:
Image attribution: originally by Inspectie Veiligheid Defensie, taken from nos.nl.
Comparing that picture with the following stock photo, it looks to me like the bullet that caused the damage entered from the front. Of course it could also be due to the aircraft flying at a high velocity.
Is this unprecedented? Or are there any records of other F-16 jets getting hit by or collide with their own bullets?