I think there's a couple episodes where either Lucas or one of the bad guys calls attention to his rapid fire "gadget." I think it was just a set screw placed in a location that would trip the trigger when the lever was closed. Anyone ever see a picture of it? I haven't.

"The universal aptitude for ineptitude makes any human accomplishment an incredible miracle." John Stapp - "Stapp's Law"
"Klaatu barada nikto"