The following is an interesting comment made by a professional Hollywood Prop Master of 17 years .....
Prop masters are the last person to hand an actor a gun, and the person who gives the actor a gun is responsible for it. You have to go through the proper procedures to show the actor if the gun is loaded or not, and if it's not, if it's plugged, when a piece of plastic or wood clogs the magazine. There are a whole bunch of scenarios, and a lot of stuff could go wrong.
People on the set being close to a prop gun is very dangerous. The blast of a prop gun can kill you, depending on the load that the gun has. Prop guns are designed not to shoot up for the projectile because they put a stop in the front, which is a certain size based on the load spring. That's to give the gun a flare look and make it look like it got fired. If anyone is inches from this type of gun, that blast can kill you.
I've never experienced anything as tragic as what happened yesterday on the 'Rust' movie set on any sets I've been on
The woman who was killed must've just been too close to the blast, but it also depends on the weapon that Alec Baldwin had.
The type of gun ties into a lot of stuff. If you have an M4 and you have a full load, the blast is going to be a little longer. I don't know the timeline of history for this story or what year they're doing - that's information I don't have, so I don't know what happened there.
All I can say is never point a gun at somebody when you're firing, and everyone nearby has to be more than six feet away. Just have it slightly away from the person you're supposed to be aiming the gun at. The guns also shoot off the shell, so you don't want to be standing to the right side of the gun because the shell comes out hot and it could hit you on the face and burn you.
I've never been afraid on set because I always double- and triple-check weapons
If a gun is not firing in a scene, there are no bullets in there. If they have a revolver where you can see the bullets, I make sure it's loaded up with dummy bullets. They have a whole band inside and you load them in front of the actor so they know what you're giving them. I also do a lot of gun checks with my actors to show them an empty magazine and that there's nothing in the barrel.