It can happen if the practice round (which is hollow) has a manufacturing defect and cracks open once it leaves the cannon muzzle.
Ibra wrote:
They made that joke with A10 thunderbolt but stopped with going slow to stall rather than backwardIt’s also bad if you go faster !
https://arstechnica.com/tech-policy/2019/04/dutch-f-16-takes-cannon-fire-from-itself/
Thank you Ibra for these two brilliant links, very interesting read!