It's just a wiki page but start here.
http://en.wikipedia.org/wiki/National_Firearms_Act
I would start with the National Firearms Acts of 1934/1968(Title II), and the Gun Control Act of 1968 ("GCA") is Title I. These are the foundation of Federal Gun Control Law in the US.
Then you could hit the Federal Assault Weapons Ban (AWB), or Public Safety and Recreational Firearms Use Protection Act, which was a subtitle of the Violent Crime Control and Law Enforcement Act of 1994.
Each and every one of these Federal Laws seek to define weapons or categories of weapons(not just firearms), and then regulate their manufacture, import, possession, ownership, and transfer, and other things as well. Each one had a defining purpose stated or otherwise, and they often had effects that fell outside of their stated purpose as well as failures to achieve the desired and/or stated objectives of the legislation.
You need to cover the stated objective of the legislation vs. the actual effects of the legislation, and challenges or court reversals/descissions that may have nullified elements of the legislation as passed.
Then if you want you can roll into what has and is currently being done in regards to gun control at the State level, but that paper is really going to grow. Then again, if it looks like it is going to come up short you could prepare and have a ready to go path for expansion. Don't try state by state, just add things by issue and correlate the issues with which states support them or supported them and later stopped because they decided against it.
These are the real good ones because they represent things that were tried and simply failed because they were a bad idea to begin with, even though some folks are still pushing them as solutions.