Really? Because self defense taught to ATKI and probably WTSDA black belts is focused on guns. One of the most basic ones is when someone's holding a gun to your back, to turn and strike. Most people simply can't react fast enough to the turn to shoot you before you're parallel with the gun, and from there, a strike can be made to the neck, or a pressure point in that area taken advantage of. Other moves deal with pointing the gun the other way or at the aggressor. Not only that, but most people only use guns as an intimidation factor. They draw attention, and are LOUD. Your average Joe doesn't have special sub-sonic ammunition and a barrel silencer for his Glock.
Shotguns and long guns are even easier. There's more barrel to take advantage of. Shotguns in videogames are nowhere near realistic, the spread pattern isn't going to hit you if you're a foot diagonal from the barrel.
You've got some dangerous misconceptions...
I've learned several versions of that gun disarm. All can work, if everything goes right. (Note that I did not say NO disarms work, nor that you shouldn't try or train them.) All can also very easily get you shot.
And I sure as hell wouldn't count on someone holding a gun on me only being out to intimidate me. That's a once in a lifetime bet... because if you're wrong, you're dead. Or at least shot. If someone presents any weapon to you in an assault -- assume they are ready and willing to use it. Any other approach invites disaster. Considering that in 2006, there were nearly 15,000 homicides, and the vast majority of them (more than 10,000) involved a firearm (See here) that seems like a bit of a losing bet. (I'm not going to parse through for assaults and attempts, nor am I going to check the Crime Victimization Survey to see about assault or attempts.)
Oh... and regarding shotguns. The shot pattern may not hit you... but you'd be more than a little amazed just how much force that blast still has, even if you're not right in front of it.
Again -- I have never said that you cannot defend yourself unarmed against a gunman. Speaking with some reasonable authority on the subject, however, I place UNARMED defenses against a gun, or even knife/stick defenses against a gun, in the category of things to do when you feel that you have no other choice. Give your favorites a try, as I suggested, with something that shoots a fairly harmless projectile like an Airsoft gun. I think you may consider it noteworthy that other people (quite a few with even more expertise than I have) pretty much agreed with my comments.
As stated previously I prefer water guns, as the water dries and it shows really how slow one is. After the water gun is done 100/100 times then the air soft could be something people might invest in. Of course if you have the money and want to start there that is good as well.
Having been in a situation or two that I believed was real here is what I did.
Walking into a local Meijers (* WalMart like store *) the person stuck something hard into my back and said stick them up. I was walking through the door and it was tight to move. I stepped forward with my hands up. The store greeter just looked at me funny but did nothing. Then the guy behind me said, "Wow, Rich with all your training and experience I thought you turn and disarm me." I replied, there were other people (* Mothers and children *) where the gun would be pointed. There was little room to move and turn the gun off line. So, my plan was to give you my wallet and then drive home and call and cancel the cards.
Another time, I was carrying $2,000 in quarters. In case you wonder there were four (4) bags with $500 in quarters in each. I carried two bags on each shoulder. They can be heavy. Most others, just carried one bag in each arm. I was just about to place them on the floor to begin filling up a change machine in an arcade that had about 150 people in it. I felt a hard round object in my back. A voice I did not recognize stated, "Raise your hands and drop the bags." I did exactly as commanded. My hands were full. If I reacted as I had room, more than likely someone else would get shot. So, I dropped the bags and raised my hands. I heard this scream as the bags hit the floor. Two of the bags had fallen in his ankle. His foot/ankle was broken and he was screaming, "Why did you do that? I am going to press charges on you." With hands raise I turned my head slowly, and looked to see what was going on. Note: None of the people in the place even came to see what was going on. None of them did more than look at my hands in the air and him on the floor screaming. I pointed to another employee and told them to call the police. We called directly, and avoided 911 as it was just in the roll out phase. The employee asked about an ambulance. I stated, that I would have, but this guy wants to press charges to lets get the police here for him first. I ended up pressing charges. It turned out that as I believed the object was a real gun and it was more than a $1,000 it was a major felony with a large jail/prison time if convicted, which he had admitted too in the police report. The ADA ended dropping the charge against me if I dropped the charge against him. I agreed under one condition, that he was not allowed back on the property.
My point to all this, is that even my experience with a gun like object to my back, I was not in the prime situation to defend myself without lots of risk to myself and or others.
I say practice a technique and see if it works for you. But also understand the limitation of the technique and when you can apply it.
PS: Even though neither of these cases was a real gun, I have other times with guns fired at me and or pointed at me or what have you. My experience states that nothing is optimum.