RE: knockdown power... fact or myth?
That has happened twice, there was another actor that got shot filming because someone swaped out the blanks for real ammo. I forget who it was though.
There was also at least one actor killed filming something with a blank. It's been years ago though and I don't remember who it was either. I think it was something to do with TV? Anyway I think he put the gun to his head goofing around and it had a blank chambered. Killed him when it went off. I have heard of other instances as well.
Having one go off near your head and having it pointed at you are too different things. The force of the gas coming out of the barrel is very directional, especially at close range. Like I said though, I think you would almost have to have contact with the target to do real serious damage unless it was a really high powered rifle.
Paul