[quote=@MelonHead]
<Snipped quote by Tuujaimaa>

You don't react to a bullet being fired at you. That would be like reacting to a sword the moment it touches your skin.

You see someone about to point a gun at you, you move. 
[/quote]

Except it isn't. Your concept does not translate adequately into this scenario.

In order for your stated scenario to work, you would have to immediately move at 250 feet per second in a direction that you are swinging the sword.