What we do is utilize the “plausibility principle“ so while it is certainly possible you may have to engage foreign troops fast roping down from a helo it is not likely very probable. Depending on who you quote for your source date,FBI, Range Master,US Govt, there is a plethora of data points. In the end the great majority of defensive handgun shootings in this Country occur inside twenty yards. We do most of our work at seven yards. We certainly expose the student to both shorter and longer drills but the bulk of our training for the standard defensive pistol course is at seven yards.