quick on the trigger

quick on the trigger

 and quick on the draw 
1. Lit. quick to draw a gun and shoot. Some of the old cowboys were known to be quick on the trigger. Wyatt Earp was particularly quick on the draw.
2. Fig. quick to respond to anything. John gets the right answer before anyone else. He's really quick on the trigger. Sally will probably win the quiz game. She's really quick on the draw.
See also: on, quick, trigger
References in classic literature ?
Always a child," said Gobseck to Gigonnet, "you are too quick on the trigger.