Ross Addiego, Doran Curtin and Reese Price -- who say they were the dolly operator, set costumer and key grip on "Rust," respectively -- are suing Alec and the "Rust" production at large ... claiming they were 3 of 7 people in the church set the day the shooting happened.

In the docs, obtained by TMZ, the plaintiffs say there were countless safety protocols that were overlooked from the top down through the entire shoot ... which they insist led up to the killing, and which they allege rocked them to their core -- emotionally and otherwise.

For instance, the three crew members place a lot of the blame on what they claim was the producers' decision to use "operable firearms" during 17 of the 21 scheduled film days ... despite the option to use alternatives like replicas, rubber prop guns, or special effects.  They also point out many alleged safety shortcuts on set ... like not properly investigating previous accidental discharges that they say occurred prior to that fateful day.

Not just that, but the crew members say Alec and others screwed the pooch with the hiring of armorer Hannah Gutierrez-Reed, even though they say she "lacked essential experience."

The lawsuit also alleges Dave Halls cut corners when it came to safety protocols. And yet, they say Alec plowed ahead with them anyway ... all of which led to the death of Hutchins in 2021.

Speaking of the incident ... the plaintiffs describe it here too. They claim Gutierrez-Reed told Halls that she hadn't had a chance to check the gun before handing it off to him and that Halls took it and told AB it was "cold," without checking. Ditto for Alec, they say.

When Halyna and director, Joel Souza were hit by the bullet during a tech rehearsal -- the crew members allege they were forced to spring into action and assist, which they say haunts them to this day and has left them traumatized. Now, they're suing for negligence and intentional infliction of emotional distress ... and asking for unspecified damages.