The main NRA organization is not a qualified charitable organization that would allow you to take a tax deduction for contributions. The NRA Foundation is such a qualified charitable organization and contributions thereto are deductible as allowed by law.
So it comes down to who you made the check out to....NRA not deductible at all......NRA Foundation is deductible. Same rule applies to the Sierra Club and its foundation.
The main organizations are lobbyist, an activity prohibited by charitable 501c organizations.
There is a separate organization within the NRA that is the "lobbying" arm of the NRA. It is called the NRA-ILA (Institute for Legislative Agenda). Contributions to the NRA-ILA are not deductible for Federal income tax purposes.
Also, from NRA website, dues are not deductible:
"Contributions, gifts or membership dues made or paid to the National Rifle Association of America are not refundable or transferable and are not deductible as charitable contributions for Federal income tax purposes."