Some gun games aren't light gun games at all, but guns attached to base that functions like a joystick.
I've never played Steel Gunners, but it appears to be that type of game... Operation Wolf and Terminator 2 are also examples of this.
I'm not sure about the workaround, but offer the info to try and get you on the right track. Does the Act Labs driver mimic mouse input? If so, you should be able to get the positional gun games to work with it.