The firing gas gun had a line running into the hand grip. As near as I can tell from watching the TV show a few years back, there were three gas guns. The firing gun, a stunt gun, and a hero version with a removable magazine that went in the grip. The hero version was for the scenes where the Green Hornet checks his gun.
The Hornet's sonic weapon, the Hornet Sting was originally spring-loaded. The problem was that the spring was too strong, and would send the front flying off. The solution was to remove the spring and have Van Williams open the sting with a flick of his wrist.
David.