But the NRA is NOT a tax deductible charity, The NRA Foundation is.  So it depends on to what organization you made the check out to.  

Also, from the Heritage Foundation website:
"Donations to support the activities of our sister organization, Heritage Action for America, may be made after making your donation to The Heritage Foundation. Heritage Action for America is a section 501(c)(4) nonprofit organization under the Internal Revenue Code. As such, contributions to Heritage Action for America are not tax deductible as charitable contributions"