"How fast should your string of shots be in between trigger pulls to be combat effective into a bad guy trying to kill you. ?" [funtoshoot]
Depends. If an active shooter is farther out, ie 20 yards or more and you are behind hard cover, you have time, precious seconds. If the assailant is in your face, you do not (police tell me most of their business is conducted at 3 to 8 feet), then you have to shoot as quickly as you can pull the trigger.
"When I'm having a "good day" I can crowd 0.20 seconds." [Mello2u]
That should do.
Check your 6.
For 20 years the sea was my home, always recall the sun going down, and my trusty friend, a 1911 pistol, strapped to my side.