From the actor's perspective it's not their job to ensure that the weapon is loaded with blanks since the armorer is supposed to just hand them a gun they've verified as safe.
not true for any production company i've ever worked with as an armorer. there is a producer that is responsible for working with me to select and secure firearms (as in, they provide secure storage location and i bring portable secure storage, my own locks, or simply deliver the firearms and ammunition each day of filming - they functionally do not leave my sight unless they are secured). even the super anti-gun actors i've worked with are forced to pay attention through a safety and firing course or they aren't being handed an actual firearm and have to use a nongun hero prop.
only the armor and the actor is intended to ever handle them, barring any assistants, and the actor is explicitly instructed on handling and inspection evertime the firearm changes hands or is otherwise moved from one controller to another. i inspect and make ready before delivery, before and after storage, before and after handing them to actors, and the actor performs in my presence and at my direction a visual and tactile inspection and we both agree that the weapon is ready for theatrical use. if we don't agree, i need to take it back for further diagnosing. this chain of custody is explicitly spelled out, isn't up for debate, and only very poorly managed productions will be lax about this.
the SAG's statement basically says as much with the additional caveat that actors are not intended to be subject matter experts and are not expected to be. however they are to obey the subject matter expert and responsible person at all times as a matter of safety.
https://www.sagaftra.org/sag-aftra-statement-rust-charges
i fully believe "Rust" was very poorly managed.
this is where i'm really mystified at how the set was run. i've done armory work for major films, shitty direct to DVD stuff, foreign films made in parts of the US or at rented studios, et c, and what i described is the general practice. the film armorer, when it comes to the weapons and munitions, is the authority on the matter and should deny, confiscate, and walk if the production company doesn't want to play by the rules. insurance and safety demands this to be the case and so does many many years of accidental and negligent deaths over the years.