The reactionary gap is a concept developed by Dennis Tueller. His research indicated that a healthy assailant, armed with a knife, could close a distance of 21 feet within an average of 1.5 seconds. This concept has, over time, become unofficial doctrine within the law enforcement community. This same concept is directly applicable to civilian self-defense. However, the overall issue with this concept is the lack of forensically proven facts. Is 21 feet actually enough? The “21 Foot Rule” assumes some reasonable ability with a firearm. The shooter must perceive the threat, process the threat, draw their firearm, and dispatch the threat. There are far too many variables, and frankly, 21 feet might not be enough. A trained law enforcement officer can take up to one second to make a response decision, this leaves fractions of a second that could be the difference between life and death. The average individual, with limited training, will take considerably longer to process the threat and make a response decision. Under the intense stress of a self-defense situation, psycho-physiological impairments will exist. Aside from competency, equipment, accuracy, and perception lag are all major considerations as well. Ultimately, the point I would like to drive home is that the “21 foot rule” is based on a competency level that many civilians don’t posses. It is important to understand yourself and your own level ability. The “21 foot rule” should be viewed as guideline with the understanding that exceptions exist. As a civilian in the self-defense world, training is paramount. Understanding pre-incident indicators and simply being aware of your surroundings will aide in closing your reactionary gap. The number one pre-incident indicator is deliberate movement towards you. Criminals are predatory and will want to close the distance between the victim and themselves. Understanding these indicators, understanding yourself, understanding your level of competency and ability, and understanding any physical limitations you may have will make the difference in closing your reactionary gaps. Stay frosty, keep shooting, and remember the “21 foot rule” is just a guideline. Know yourself and stay aware! Get off of the X!