It's time for the film industry to stop playing around.
Actors who handle guns on set should be trained in gun safety. NO EXCEPTIONS.
I don't care how famous the actor is. I don't care that the actor is a complete idiot. Gun safety should NOT be a transferable responsibility. If something goes wrong, it's not only the armorer's fault, it's also the actor's fault.
Would I give this actor a pass this time? Fine. But NEVER AGAIN. The armorer should be responsible for knowing how the gun is loaded and what it's loaded with. The actor holding the gun should be responsible for knowing how the gun is loaded and what it's loaded with. "It costs too much to train the actor" is NOT AN EXCUSE. If the actor is too stupid to learn gun safety, hire smarter actors or give the actor a toy gun, not a real one. Non-firing replicas exist, there's no reason an actor too stupid to handle a real gun can't be given one. Take out the orange tip in post, no reason you can't chroma-key on orange near the actor.
I've got a degree in tech theatre. I know how stupid actors can be. I've also been there when there's been a gun on stage, I've seen guns modified to be unable to fire anything but blanks. Magazines can be blocked, chambers can be modified to not accept anything but blanks, do that and the breech won't even close on a live round, a revolver can't even be loaded if you do it right. Sure, a blank can still kill when the actor is stupid enough, but only at near-zero distance (ie Jon-Erik Hexum) but you'll never see an AD dead from a blank fired across the set.
So, train the actors, and hold them responsible for pointing guns at people and pulling the trigger.
