I am 63 years old and have studied Judo, Shotokan Karate, Taekwondo and Aikido. I also suffer from emphysema. The reality is you cannot learn to defend yourself from a book or a dvd alone. You must put the time in practicing. As you practice various tactics visualize an opponent, unless you have a training partner. If you are in aphysical attack you do not have time, normally, to pull a gun. Nor do you have time to pull if someone is rushing you, they will close with you too quickly for you to pull. If all else fails go to your back with your feet toward the opponent, assuming only one, This position is very defensible and it will allow you to pull your weapon. Random thoughts from one of the old guys...

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Retired Marine Gunny