I'll pass on the NRA suggestions. Apprently, it escaped their notice that there are also libertarians on the ballot. They do the voters of the US a disservice.
The second problem with the NRA ratings is that they are wa-aaaaay too generous with passing out "A" grades.
Take John Boehner for example. As speaker, he recently allowed renewal of the Undetectable Firearms Act of 1988 on a unaccountable voice vote with only 10 our of 435 representatives present.
Boehner's NRA rating? A+.
The NRA also doesn't make their criteria for the grades readily available, or the candidate responses.
They also shower some of the biggest statists in the Republican Party with contributions.