Rarely today is the need for a real gun on a set, there are prop guns with look and moving parts for close work and all the effects can be added in. I really doubt he can pull off his all rubber guns idea beacause fake is relly obvious in close ups. Also I doubt he would be hiring inexperienced and incompetent armorers and safety officers on the cheap as well as understaffing. Anyway Duane blew his respect out the door when he went goo goo over Captain Depends.
You could always just remove the firing pin from a real gun. But then, as thousands of actors from the old westerns could tell you, you could also just CHECK YOUR GUN!