You can just cross out your name on the subscription label. The folders may include pamphlets, newspaper clips, and other miscellaneous materials. Ask the librarian if there is such a file, and if you can donate materials for it. Libraries usually have community bulletin boards, as do organizations such as the American Legion and the Veterans of Foreign Wars. Keep an eye on the bulletin boards and, if the public is allowed to post materials, stick up a flyer from your local pro-rights organization.
Some libraries set up table displays from time to time.
If you see that your library has one, consider offering to set one up about gun control. Before speaking with the librarian, examine what other kinds of displays the library has, and try to design something that fits in with what the library is already used to. The librarian will probably be more receptive if you can provide a balanced set of materials, rather than information that just reflects the pro-rights viewpoint. Before you write a letter to the editor of the local paper, read the letters to the editor column, and see what kind of letters get printed. Before you visit a Congresswoman's office, study her voting record.