First: The NRA is a weaksauce gun 'rights' organisation, which is hated by just as many pro-gun people as anti-gun people.
Second: You'd need to overturn [*Warren v. District of Columbia*](https://en.wikipedia.org/wiki/Warren_v._District_of_Columbia) and [*Town of Castle Rock v. Gonzales*](https://en.wikipedia.org/wiki/Town_of_Castle_Rock_v._Gonzales) to force the police to have a legal obligation to protect people, and are open to both civil and criminal lawsuits should they fail to do so.
Third: IIRC wouldn't raising the voting age basically kill the democratic majority in nominally solid-blue voting districts?