4 seconds 

This is my son, a State Patrol trooper, practicing drawing his full-size service weapon (with light) from (a level III retention, I think) holster, firing, ejecting the empty magazine, inserting a second magazine from his snapped duty belt, chambering a round, and firing again. He did it in four seconds. Both shots on target at seven yards (21 feet). Three seconds from 1st to 2nd shot.