Rule of thumb is...if you have to remember 3 things to protect yourself from an attacker, you may as well consider yourself down!
1. Oh shit, I'm under attack...get the gun
2. What is the combination to this lock
3. cock the gun to load the chamber or turn off the safety or load the gun
4. take aim...too late, the criminal has already accomplished his original intent!
What good is a gun as protection if it isn't loaded and accessible?
A fire extinguisher would work better, either that or just throw the gun at the perp.