It's time to discuss the very real reason that most Americans keep guns in their home.
It is of course, to defend against the very real menace of Zombie Attack.
However, the true problem is that assault rifles and pistols are actually the LAST thing you want to have in order to combat the threat of Zombies.
(Dealing with the Zombies on the Flip)
First of all, let's talk about penetration. As we know the only way to take care of a zombie is to shoot them in the head, or otherwise destroy the brain. Even Gun Aficionados agree that handgun and assault rifle rounds are not ideal for taking down zombies. Typical hunting calibers and rifles are much more likely to deal with your standard issue zombie.
Next, we'll discuss Trigger Discipline. When you have a fill clip of rounds, the ability to fire as many rounds as possible really fast leads to a poorly trained individual doing just that. Well, wasting rounds in a survival situation is not going to be in your best interest. The feeling of invincibility such a tactic provides will only last until that ominous little... click.
Finally, you want to be able to stay as FAR as possible from zombies. .223 rounds are not ideal for this situation. The round isn't much good beyond 200 meters, and even that's pushing it. Remember, even one bite from a ravenous flesh eating zombie is a death sentence!
At close range of course, your best bet is not an assault rifle or handgun, since the difficulty of reloading in close quarters and the very real added stress of attempting to target and breathe with a moaning monstrosity approaching is life threatening. A shotgun or big heavy stick is probably much better at this point, and neither one would be banned by an assault weapon and handgun ban.
Of course, this assumes Standard Romero Zombies. If we're looking at 28 days later zombies, we're pretty much fucked any way you look at it. However, even in such a situation, an assault rifle would only attract zombies.
Therefore, we can rest assured that banning handguns and assault rifles with large magazines will not have a deleterious effect upon your survival when the inevitable zombie apocalypse happens. Of course this assumes that you will work together with your fellow human beings to survive in this situation. I mean, it's not likely that anyone in such a situation would contemplate shooting fellow humans and taking THEIR stuff because of the breakdown of civil society... right?