I would expect a document of this type to be central to Baldwin’s defense. This is a union local of International Alliance of Theatrical Stage Employees (IATSE) union worker’s job description for an armorer…
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DUTIES
Armorers are responsible for the transport, storage, and safe use of all weaponry and firearms on film sets. It is illegal to use NFA (and sometimes Title 1) firearms on set unless a licensed Armorer is present. Armorers are highly skilled individuals, with a great deal of responsibility for the safety of the cast and crew. They ensure that weapons are used safely and correctly, and that those who handle them (usually Actors) are competent to do so. They liaise with the Production Designer, Properties Master, Producer, Director, Camera crew and Actors, and they may work with a Fight Director and Stunt team if they are employed on the production.
The Armorer on a Film/TV set is present to ensure the safety of the cast and crew when weapons are used. The Armorer also ensures the production is able to get the best possible look of blank firing weapons.
The Armorer should know what the director wants to achieve and help them carry it out in a safe manor. The actor/actress who will be firing the weapon should be instructed on the particular weapon(s) used as to the dangers and safe use. They should be instructed as to where to aim and how many blank rounds they have. The Armorer should be aware of and make the cast and crew aware of where the spent shells will eject.
The Armorer should immediately collect all firearms and safely secure them after each discharge. The Locations Department on a Film set should be in direct contact with the police service bureaus and make sure they meet the Armorer and that the Armorer has an opportunity to show the officer the plugged weapons and receive permission to operate the weapons.