> there isn't an alternative organization that is working to protect second amendment rights that I'm aware of

There are a few others: Gun Owners of America (GOA), Citizens Committee for the Right to Keep and Bear Arms (CCRKBA), etc., but perhaps the biggest and most effective (though not nearly as large as the NRA) is the Second Amendment Foundation (SAF) - who effects most of the change they desire through lawsuit.

The two largest gun rights cases of our era (to date) are DC v Heller and Chicago v McDonald. Both of those cases were the result of a suit initiated by the Second Amendment Foundation. They're also better about keeping themselves single-issue than the NRA, which is good for me personally because outside of gun rights and safety, I disagree with the NRA on very little.