The fatal film-set shooting of cinematographer Halyna Hutchins by actor Alec Baldwin has reopened the debate about using guns during movie making.

With dozens of movies and hundreds of TV series produced in the US every year, many of them featuring weapons, safety is a huge issue.

AFP looks at how firearms are regulated in the industry.

What are the rules on using guns?

Strict and very detailed rules are written in a “safety bulletin” issued by the Industry-Wide Labor-Management Safety Committee, which represents staff and managers working across the motion picture and television industry.

The document contains a number of edicts and warnings, chief among them – written in bold, capital letters at the top – is: “Blanks can kill. Treat all firearms as though they are loaded. ‘Live ammunition’ is never to be used nor brought onto any studio lot or stage.”

However, the safety bulletin is not binding and has no legal underpinning.

There is no federal US law specifically addressing the use of firearms on set, though most states have rules applying to workplace safety or firearms in general.

Who are the armourers who control guns on a set?

“There is no film gunsmith school” and no licensing body, says Guillaume Delouche, who has been working as an armourer in Hollywood for three decades.

“Usually you become an apprentice in a gun rental company and you are sent to the shoots, and you learn in the field,” he says.

California is the only state to require that “all people in charge of weapons” on a film set, whether armourers or propmasters, undergo a specific four-hour training course on gun safety.

Is there a difference between firearms used on set and real weapons?

The guns we see on screens are one of two things: either dummy weapons made of plastic or latex, or weapons capable of producing a detonation.

“When we say a ‘prop gun’ on a film set, we mean a rubber or a replica that does not fire,” says SL Huang, a stuntwoman and movie armorer.

“We do not mean a blank firing gun. We call blank fire guns ‘real guns’ because . . . they are real.”

Automatic and semi-automatic weapons used onscreen are modified with a cap in the barrel.

Manual weapons, such as revolvers or Winchester-style lever guns used in Westerns, are used as is, says Delouche.

Are live bullets used? What is the difference with a blank cartridge?

“What we call real ammunition is a real bullet, a cartridge that contains a projectile that will finish its course in a target after passing through the barrel,” says Delouche.

In the cinema, “live ammunition is used in extremely rare cases, and only on shooting ranges or appropriate places”, never on a soundstage, he says.

A blank cartridge, on the other hand, contains no projectile – just a charge of powder and a primer that sets it off to produce a detonation.

There is also a third category of ammunition: dummy bullets.

“They are not real bullets that have been neutralised but bullets made to be inert: there has never been a primer or powder,” explains Delouche.

These bullets are used as props when a close-up is called for – for example, when a weapon is being loaded.

Witnesses to the ‘Rust’ shooting say the phrase ‘cold gun’ was called as the weapon was introduced. What does that mean?

In cinema jargon, a “cold gun” refers to a completely empty weapon, without even a blank cartridge inside.

It can be handled without danger of ignition and does not pose a threat.

“When I am using a cold gun or a cold gun with dummies in it, I am very clear with the cast and crew about it,” says Huang.

“I physically open [the gun] and show that the weapon is cold to the actors, the crew.”

When the shoot switches to “hot guns” – those loaded with blanks – announcements are made repeatedly, so that everyone on set is aware.

“We only load the exact amount of blank ammunition needed for the scene. We only have hot guns on set for exactly the amount of time it takes to film the gunfire,” Huang says.

How effective are these safety rules?

Since the 1993 on-set death of actor Brandon Lee, who was accidentally shot with improperly made dummy bullets, “there has been no incident with firearms on a set,” says Delouche, but more than 40 in other areas – construction or stunts, for example.

Huang insists the multiple levels of checking and rechecking ensure a mistake does not become a tragedy.

“Our procedures plan in mistakes, actor error, etc. There should never be any single fail point; if anyone makes a mistake, there are many multiple other things backing up the safety,” she says.