Prop Guns vs. Real Guns
A 'prop' gun is just that. It is incapable of firing live or blank ammunition. Normally, you should be able to use an airsoft gun for your actors because they look real and will not fire any type of ammunition. These can be purchased over the internet, on eBay, Amazon, etc.
Real guns are firearms that have been modified to fire blank ammunition but these are still 'real' guns and are subject to all laws concerning possession and transportation. While there are certain 'replica' type firearms available that fire 8mm safety blanks, the overwhelming types of blank firing weapons are real guns.
If you plan on using blank firing guns on your project, you will need a licensed weapons specialist for all types of assault weapons, .50 BMG, machineguns, short barrelled rifles and shotguns and any types of weapons larger than .50 caliber.
An Entertainment Firearms Permit is the minimum permit required by the state to handle, possess and transport revolvers, most pistols, bolt or pump action rifles and most semi-auto and pump shotguns.
It is illegal to allow anyone to bring their own firearms to a set unless that person has the appropriate license(s) or permit(s). Ownership alone is not sufficient to comply with the law(s) regarding theatrical productions.
Insurance companies will recognize and accept licensed/permitted weapons people and many times will lower your premiums because you will have an expert on set during gunfire sequences.
When in doubt... Hire an expert!