Why do people act like it would be so easy to get an illegal gun if the most deadly guns were illegal? I agree it would be possible for years, until the police eventually confiscate them all, but I definitely don't think it would be easy. I think most people don't really have any idea where to find an illegal gun...
It's not at all difficult to acquire marijuana despite decades of prohibition.
Can you grow guns in your closet?
It is not very difficult at all to make guns out of common household objects (
http://en.wikipedia.org/wiki/Improvised_firearm). You can find guides online on how they are made. Generally they are less reliable than professional weapons (and frequently must be loaded one-shot-at-a-time), but on the other hand it's easy to disguise them as other objects, especially flashlights.
The more significant issue is that, like marijuana, the government is losing a large source of taxable revenue; that the government, by banning it would make the quality worse and the object more dangerous to the user; that criminal groups would gain power by successfully selling guns; and that the government really couldn't ban it anyway, because of cultural norms (which doesn't really apply to marijuana; there aren't broad swathes of the country where simply due to the composition of the population anti-marijuana laws go unenforced, but such an area would exist for anti-gun laws).
If gun-trade-gangs are anywhere near as successful as, say, drug dealers, it wouldn't even be
that hard to find a professionally made weapon (especially considering way more people want guns than drugs) -- certainly if you're persistent enough and are surrounded by like-minded people, even in very urban areas it can't be that hard to find a friend of a friend.
It is impossible to effectively ban guns in the US, and were such laws to be enacted the effects would largely be negative ones. It is possible in theory to enact stricter gun control laws than exist today, but in practice that's also impossible because (to cite an example) a smaller percentage of the population want stronger gun control laws than voted for McCain (who is, I shall remind you, considered to have lost 'in a landslide').
