The problem is double tap is not a reference to a head shot but to just two quick aimed shots at the same sight picture. It can be the head, chest, legs, gut etc. By that you fire the first shot and then quickly re-aim your sights back at the same target and fire a second aimed shot. It is usually done in close succession to the first shot. This used as part of the Failure Drill/Mozambique Drill/Failure to Stop Drill where a double to the center mass is fired and a aimed head shot is then fired to drop the target if the two to the chest do not stop the target.
The problem is double tap is not a reference to a head shot but to just two quick aimed shots at the same sight picture. It can be the head, chest, legs, gut etc. By that you fire the first shot and then quickly re-aim your sights back at the same target and fire a second aimed shot. It is usually done in close succession to the first shot. This used as part of the Failure Drill/Mozambique Drill/Failure to Stop Drill where a double to the center mass is fired and a aimed head shot is then fired to drop the target if the two to the chest do not stop the target.
Who watches the watchmen?