Part of the problem is the way people are reporting this. In technical terms ANY loaded gun on a film set (blanks or live ammo) is considered a "live gun".
The report I read was that the stunt double "misfired" and fired two "live" rounds the day before, when the gun should have been empty. We don't know if they were real bullets or blanks because of this hazy "live" definition, although there are some reports that they were real bullets that whizzed over crew's heads and this is one of the reasons the stage hands walked off in protest the next morning.
It certainly sounds like there was a real bullet in Baldwin's gun that fired the fatal shot. Although there ARE ways a gun with blanks in it can fire a projectile. In the famous case of Brandon Lee, it was determined that the slug from a dummy round (used when someone needs to be filmed handling or loading a gun on camera) broke loose and stayed in the barrel when it was unloaded, and when the gun was fired with a blank cartridge, the dislodged bullet was propelled.
It's a very good question as to WHY there would be ANY live ammo on a film shoot. Sure, for a western you have to show a real looking bullet for the camera, and show an actor loading a revolver, but I just assumed these were dummies with no primer or gunpowder.
As a stage hand in the 80s I never worked on a film or TV show (just theater) so I'm not familiar with protocol, and I'm sure that protocol would be stricter today. However they're out in the desert, on a dude ranch, and I wouldn't be surprised if maybe the gun aficionados on the crew and among the actors do some target practice with real rounds during their breaks, so there might be real ammo around, but I honestly can't understand why any real ammo would be anywhere on set. Nor can I understand why the armorer would load any gun used as a prop with real ammo.
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