The NRA was founded during the time of the American Civil War. Initially it was intended to improve the marksmanship of Americans. The founders of the NRA were dissatisfied with the ability of Americans to kill their fellow Americans during this war. The fact that this didn't end this organization at its beginning is one of those things that I fail to understand.
It is important to note now that as far as this initial goal is concerned the NRA has been a failure. The mass shootings which characterize America and America alone show that "accuracy through volume of fire" has a lot more bearing on the effectiveness of mass shooters than accuracy itself. The Supreme Court's recent ruling on bumpstocks says a lot about the philosophy of gun fanciers in the United States and I can't see such a ruling taking place anywhere else in the world, even war-torn places where gun violence is even more endemic than it is here.
It probably goes without saying that the fact that the NRA has been so ineffective at improving marksmanship in the US is one reason that Donald Trump is still alive.