I can’t believe someone hasn’t stood up a usable prop gun company that would solve this issue. Doesn’t seem difficult from an engineering perspective.
Replicas that have working feed/discharge mechanisms but dead ignition (inert firing pins). Eliminate the live/dummy/blank issue at its source while keeping the ability to film loading/unloading without having to use alternative weapons that could have live fire capability. The replica system should be the only thing allowed on a set, ever.
Alternative spark and smoke source, electrically fired with an internal source that is decoupled from the ammo system entirely. Visually representative but low noise to reduce hearing risk. Audio can be dubbed in later. Weapon could probably provide a recordable metadata that audio techs could use to easily insert the proper gunfire location/direction/echos/etc.
RFID system that validates the weapon as an authenticated replica tied into a secure database.
Interrogation scanners/stations that can be used by the armorer and a second layer while on set before, during, and after shooting to validate replica status and chain of custody. Every actor scans their weapons walking into a scene for a visual approval that it’s safe to aim at anything other than the ground, every time. This could probably even be expanded to RFID wearables that track hand offs between people on set to further establish chain of custody.
Storage system that ties into RFID/audit system that checks guns in and out with approved armorer credentials. The system flags weapons as tampered if the case isn’t opened/closed according to procedures and credentials. Doesn’t eliminate the risk of weapon alteration entirely, but would reduce the list of suspects to the armorers that have the credentials to check and approve the weapons in the system. Also ensures alteration/chain of custody would almost entirely result in a murder charge because there is no real possibility of an accidental discharge through negligence. It would only result from a modification of the replica or tracking system.