The recent tragedy that involved Alec Baldwin accidentally killing a cinematographer on the set of Rust has many wondering what exactly a “prop gun” is, the answer is a little complicated.
To be clear, the gun that Alec Baldwin was wielding when he accidentally shot and killed Halyna Hutchins was a real gun. There is no sugar coating the fact that this was a real firearm on set that was loaded with real ammunition. The gun is being referred to as a “prop gun” because that is what it is, the firearm used as a prop for the film.
Not all prop guns are real guns, like the ones on the set of Rust, some prop guns are plastic replicas, others are made of foam, some are real guns that have been rendered inoperable.
Plastic guns are often used for set pieces in films. This kind of prop-gun is cheap, non-functioning, and generally seen in the background of movies and TV. A notable exception to this rule was in the film Lord of War, the film needed thousands of AK-47 rifles for a scene and it was cheaper for the studio to buy an entire lot of them and then resell them as opposed to building thousands of replica arms or having an effects team animate these digital assets.
Real guns are used in films when they are used often by characters. These should be unloaded, in fact, real ammo should not be on the set at all while filming with these. When guns need to be used for a scene they are often loaded with blanks and adapted by pro-gun smiths to fire blanks.
BB guns and green gas guns are used more often than real guns in most films. We all know what BB guns are, as for green gas guns, these are replica arms that do all the same things as normal guns except fire a round. When these firearms are used in films they need to have an effects team animate in muzzle flash and casing ejections, these guns will cycle on their own but for the sake of realism in movies and TV, these effects are added.
Scott A. Reeder, a real props professional, went on to explain in one of his videos all the details about the guns you see in TV and movies.