If there would be chaos, you would optimize your survival chances by having a rifle and having trained a lot with it. Choose one with metal sights [the ones bolted to the rifle at the top front and the second closer to you], and a good scope, so that if your scope gets damaged you would have an extra chance. Pick ammo type after what is normal in your area and cheap, so you can buy lots. Never knows when the world is normal again. By choosing a popular ammo amongst other people you can also take their ammo if you need to! [I would only do that if they were dead, gone or bartered with me. One have to uphold morale].
Now, by rifle I do not mean the AR-15 thing, even though they would be good in close combat. Never having hold one I guess they are heavier and more troublesome at long distances, not to mention the magazine that sticks out so unconviniently. But there are many fans of these, especially in the US. Most normal hunting rifles have small magazines that would let you take down your target anyway, and half automatic ones are around. The normal ones are more reliable than machine guns, and easier to maintain. Also, having not so many but enough shots to take out big animals, you would not spray to much ammo on them, but learn to consider each shot carefully.
Monotony: If guns were to be banned for the civil, good for us really. Less people to think about with guns out there! But you [and I] would hide our guns away in a VERY safe place, perhaps out in the bush, where chances of survival would be best. With a small team of course, and hideout. We are stronger together, but not too many.
Morphious: Letting almost everyone own almost any gun in America for "self defense" sounds strange to me. Are not the ones you defend against robbers, criminals and crazy youth, who loves that the guns are so easy to get hold of? Most ones who are shot never carry the guns on themselves anyway, even if they are in their own house, making it pointless, because it is so easy to take civilians by surprise!
America has one of the highes murder rates in the world. That is not self defence. Look to Canada, where they are not so afraid to lock their doors at night. Let handguns be banned for the safety of all
!
And also, the american government [and many more] don't want the best for their people. That is why we are here. They won't be bothered that their peoples are decimating, when it is mostly the poor people that gets shot.
BTW, I have never owned a gun but very soon will

[legally] I have shot very little with hunting rifles but I know they are the right kind for this environment in Europe at least. And I love to read about the subject, finding peoples experiences all over the net.
Check out
www.survivalistboards.com for almost any info you need for practical survival.
Edited some grammars