What is a prop gun and how does a blank cartridge work? An explainer

A prop gun fired by Alec Baldwin on the set of the western film “Rust” killed the film’s cinematographer, Halyna Hutchins, and injured director Joel Souza. But just what exactly is a “prop gun,” what is a blank cartridge and how can they be so deadly?

The term “prop gun” includes a variety of weapons, including nonfunctioning guns, cap guns and fake guns constructed of wood, plastic or rubber. The term also can mean real guns modified to fire only blank cartridges, which can pack a punch — and even result in death — if fired at close range.

Blanks are shell casings loaded with gunpowder. They lack the deadly bullet point, which is usually replaced with cotton or paper wadding. When blanks are discharged, they create the sound of gunfire, and the gunpowder combusts, causing a muzzle flash. The force of firing a prop gun provides the shooter with real recoil.

At close range, however, prop guns can cause injury or death.

“Even without a projectile, the burning flame, hot gases and debris from burned and unburned flakes of gunpowder create a very real hazard at close distances. However, these hazards are based on physics and can therefore be predicted and controlled by someone who knows what they’re doing,” wrote firearms safety coordinator Dave Brown in a 2019 American Cinematographer article titled “Filming With Firearms.”

In addition to blank rounds, dummy rounds sometimes are used on set. These are designed to look like real bullets but contain no gunpowder. They can be used in closeup shots for effect.

When actor Brandon Lee was killed in 1993 on the set of “The Crow,” The Times reported that the projectile tip of a dummy round was accidentally lodged in a gun chamber; it was then propelled out of the gun by a blank cartridge.

A union representing film crew members said a “single live round” (which can mean a blank) fired from the Baldwin weapon is what killed Hutchins and injured Souza.