Start with 7 rounds in your holstered gun, and 2 7 round magazines in your mag pouch. total of 21 rounds.
You are 7 yards form the target(21 feet).
The time to beat (eventually) is 21 seconds.
You need a shot timer but for starters you could use a stop watch
At the buzzer shoot the 1 once the 2 twice the 3 three times the 4 four times the 5 five times and the 6 six times. You will need to reload after the 1st shot on the 4 and after the 4th shot on the 5.
So it gets its name because of the Casino game black jack or 21
The goal is of course no misses
We use this as a baseline for our students. they shoot it and write there time on the target. The next time they shoot it they get to see how much they improved in accuracy and speed.