It seems there are limited rules and 2 different sets of guidance for it and different productions approach it differently.
Quite a few work with all firearms related items inventoried in and out, every movement logged and hard isolation between firearms used for live ammo and those not sometimes to the point of having 2 different companies. But doesn't seem to be a fully legally enforced thing despite several actors/armourers in the wake of the incident coming out saying it is.
The main thing though is the firearms handling on set - no one should be handling a firearm without sufficient training in the basics or if that isn't possible under direct 1:1 supervision as you see at turn up and shoot ranges (which unfortunately doesn't eliminate accidents as per the instructor who got killed by a child with a fully automatic Uzi). A weapon should never be pointed at anything you don't intend to shoot especially if the person holding it has no idea as to the status of the gun for themselves and it is a fairly simple thing to check whether a round is loaded if you do need to use it in an unsafe manner for scenes which don't involve shooting the weapon - largely checking each round as to whether it is live or not isn't necessary though not a bad thing to do until it comes to scenes where firearms are being discharged.
