When I was first walking the beat back in 1978, shooters would phone up the police and tell us where they were going to shoot that day in case we got calls from the public. These days I doubt if the police could be bothered to take down the details.
When you have a professional film company shooting action scenes with weapons then its probably obvious what is going on to both the public and the police. However, as the camera gets smaller then I can see how easy it would be for a member of the public to make a mistake and call the law. If there is any chance that your filming might generate calls then do telephone the police and tell them what you are doing. Ask them to create an information serial and provide a mobile contact number, detail of the weapon, actors etc. If they get calls hopefully they will be linked to your serial and your phone may ring before the police arrive.
These days the police will respond to all firearms calls. When they do then its 99% certain that the only policeman who is going to check it out will be armed. They have various options for doing this but they are likely to want to dominate you very quickly and aggressively. We all know what to do if they show up don't we ? If you don't then allow me to make it clear. Drop the gun, walk away from it and put your hands in the air. Then follow precisely the instructions given to you.
I only point this out as people without any criminal intent, often do the reverse and walk towards the officer trying to explain what they are doing and waving the gun around. Never ever point it at the officer or anyone else or discharge it to show its a blank, air pistol etc.