The 21' rule is a general principal that states that an individual with a holstered weapon can not draw, aim, and fire effectively before a man armed with a knife can run over and stab/slash them. It is a fact based statement derived from incidents' where law enforcement officers with their weapons holstered were unexpectedly attacked, when answering a dispatch call, by an assailant armed with a knife. Even though the officers were trained to draw and fire, their cognitive delay (the time it takes for the brain to decipher and correlate data under stress) resulted in them being stabbed and/or slashed before they were able to bring their weapon on target.
It is a training scenario commonly used in the Tactical Force Training Division of KM Alliance. At our school we use 32 cal. CO2 R.A.M. Pistols and Shock Knives to simulate the situational threat. Even in a civilian setting you could be faced with this situation... You are at home, someone breaks into your home in a home invasion, they burst through your front door and attack you, can you get your gun, aim, and fire effectively enough to stop them. And before you say "Oh that would never happen.", it actually happens way more often than you would think.
We go through several tactical training exercises such as this, usually scheduling one 4 hr. focused seminar every quarter. It gives us the opportunity to bring our students training to a more extreme level.
The 21 foot rule is taught to law enforcement. A man with a knife within 21 feet can run and stab you before you can shoot him. That's about the width of a average residential road. And that's why you keep your distance when confronting a person with a knife.
The 21 foot rule originated from law enforcement studies of violent encounters where a law enforcement officer was attacked by a knife wielding suspect. They found out that someone with a knife who is within 21 feet can close the range and stab a man with a gun before he can draw and fire his gun - even highly trained officers.
This fact is drummed into police training and incorporated into many self-defense schools so that the trainees know that drawing their pistol is no longer an option in that scenario and must compensate for it either by using disarming techniques, introducing some sort of obstacles between the attacker and yourself such as throwing a chair in his way, or back pedal and increase the distance.
As others have detailedly stated it’s a knifeman’s running distance between the draw and firing of a gunman. It mostly applies to gunmans though since it’s very unlikely that you’ll have to use self defense again a gunman that hasn’t drawn their weapon yet. Once drawn the 21 feet rule no longer applies to the gunman. At that point it’s best to trick them into covering the distance for you(then applying empty handed art), distract them or trick them into going farther away before running to some kind of cover.
You cannot legally shoot the attacker if he is beyond 21 feet from you, because then you have the chance to get away without having to retalliate.
Definetely for sight and vision .
One man has knife the other a gun.
