All gun-related legislation originating in the U.S. House of Representatives is first referred to the House Judiciary Committee. The Chairman of the committee is Lamar Smith, a pro-2A Texan that has expressed no interest in additional gun control. In addition to your own Representative, of course, the members of this committee would be the next most important contacts to make.
Our goal for any anti-gun legislation is to "die in committee" - and for our purposes that is the House Judiciary Committee.
View the membership and committee schedule at:
http://judiciary.house.gov/index.html