The NRA is, and always has been, bi-partisan.
I find this to be the same philosophy as being a moderate, and Rush Limbaugh has the best definition thereof. It is so easy anyone can do it. It takes guts to take a stand.
Oh, the NRA DOES take stands. However, the stands they take are not as far reaching or pleasing to conservatives as other gun-rights groups, such as the GOA.
By the way, GOA is “officially” b-partisan, too. Most, if not all, of these single issues/ratings groups are - be it NRTL, NARAL, Gun Control groups, etc. They pretty much have to be, especially when it comes to endorsements.
Over the course of an election season you will nearly always see a decidedly conservative group endorse a DEM and a decidedly liberal group endorse a GOPer. That way, the group(s) can claim they are not officially a part of the apparatus of any political party.