I think there are a ton of other ways to film this and examine the site picture without putting a gun in perfect alignment to your head. The only way I’m looking at a barrel is if its outside the weapon.
Sure, he probably cleared this gun, but you really should treat every firearm as if its loaded, all the time. If you need to examine a weapon like this, disassemble it so there is no way it can go off.
It only takes one moment of confusion to end in a tragedy.
This guy is lucky he had time to dodge the projectile kicked back at him. This is what makes shooting explosive targets so dangerous. Make sure you are shooting from cover, there are no loose objects around to become shrapnel, and you are a good, safe distance away before you pull the trigger on a reactive target down range.