If you have a ccw weapon and just want to get your hands free and 2 meters of distance again, and have no classical martial arts background, Krav Mager Maor might be right for you: Easy to learn and effective.
If you also want to be able to finish a fight and fight on the ground, jiu-jitsu is my recommendation. But this takes time to get good with. If you finally are, you cold be more effective on short ranges with your body than with a gun...
and here's just the standard boiler-plate from my website:
The martial arts can be divided into three fields: Self-Defence, Martial Sports and so-called "Soft" Martial Arts.
Self-Defence need not be graceful, fair or an appropriate subject of competition. It need only be effective and easy to recall. Focussing on real-life situations, self-defence systems need to provide for appropriate and reliable ways for a suprised defendant to protect him/herself without taking risks. Self-defence therefore rather be radical and simple. The best self-defence system I know is
http://www.atk.at.
Martial Sports have a totally different aim. Though they mostly originated from real-life combat techniques, they have changed in order to give a forum for fair competition. Sometimes they are as far away from self-defence as olympic fencing is from an ancient swordfight. They give rise to tremendous athletic and acrobatic performance. Such Martial Sports are e.g. TaeKwonDo, Judo, Karate, Wrestling and (Kick-) Boxing.
"Soft" Martial Arts should not be misunderstood. Although they focus on the art as such, they can be very tough. Usually they take very long to be learned and don't provide a forum for competition. E.g. Aikido and Chinese Kung-Fu Styles are usually neither practiced for athletic nor self-defence purposes. However, they can be extremly demanding and effective once one has reached master's skills.