Jerry Miculek shoots two types of ammunitions - 200 gr at 2200 fps, and 395 gr at 1520 fps - to see how .460 Magnum performs
https://www.youtube.com/watch?v=G_NKKRHdWR0
You can see a small explosion in 3:01 and 4:20. This is caused by airs compressing rapidly in a closed space. condensing heat in a small area leading to explosion.
From: Miculek.com