The question the debate will center around: Is it the duty of the Government to regulate the sales and ownership of certain firearms?
No. The Constitution is very clear and has been incorporated into the states. Then I would break down the Second Amendment, show how the "well regulated militia" actually relates to the amendment (how "well regulated" at the time of writing meant "well trained," how practically all able-bodied males were/are a part of the unorganized militia, and how the "militia" is simply part of the justification for this right and the need to not have it infringed upon), and then define what "infringe" means and how regulating the "sales and ownership" is an infringement and why it doesn't pass strict scrutiny.
Then there's gun cases, here's a few good ones from US vs Miller (taken from the wiki):
"In the absence of any evidence tending to show that possession or use of a 'shotgun having a barrel of less than eighteen inches in length' at this time has some reasonable relationship to the preservation or efficiency of a well regulated militia, we cannot say that the Second Amendment guarantees the right to keep and bear such an instrument."
and
"The significance attributed to the term Militia appears from the debates in the Convention, the history and legislation of Colonies and States, and the writings of approved commentators. These show plainly enough that the Militia comprised all males physically capable of acting in concert for the common defense. 'A body of citizens enrolled for military discipline.' And further, that ordinarily when called for service these men were expected to appear bearing arms supplied by themselves and of the kind in common use at the time."
Obviously I disagree with the end ruling of the case, but one can use these quotes to directly show the flaw in the final ruling. The first shows how weapons that would have a use for a militia can't be regulated (issue with the case was one of "no evidence") and the second quote reaffirms via court case what was discussed in the first bit about militia service and how militiamen have to be able to supply their own weapons.
For a third and final point I would show how prohibition hasn't worked. Whether it's the Eighteenth Amendment, the "War on Drugs," or the various gun bans around the world (great place to show how around the world crime in general has gone up with gun bans), prohibition doesn't work. Can also show how issues have gone down when the bans were lifted (prohibition crime, Portugal drug issues, and overall crime in DC since I'm not sure what's up with Chicago).
Then I would be prepared to deal with things like how many "kids" are injured/killed per year (includes kid gang-members and typically the numbers include those up to either 19 or 24 depending on source), the gunshow "loophole," assault weapons (and how it's a made-up term), GFZs (and how they don't work), and some other standard hoplophobe standard arguements/misinformation. Probably won't use all of these, but better to be prepared for it in case the other person uses them than to be blindsided by at least the common arguements.
The bigger issue is trying to cram such a large subject into only five minutes for the debate. Oh and gunfacts.info is a great site for a bunch of information in a consolidated place.
