We’ve had access to capable guns for a very long time and mass shootings only became a thing in the 90s.

Dude, don't. This took 2 seconds to find. There's more that I'm aware of just from memory too. Also, the white guys thing.

The manual of arms being different isn't a big a deal. We train people on everything between pistols and belt fed machineguns. There's no reason to expect the manual of arms would be a large barrier to an actual militia fighting alongside the military. In fact standardizing an official "militia rifle" would help prevent people from showing up with 4 or 5 distinct modes of firearm.

I actually agree about the social problems leading to a larger number of events. But that's not working, it sounds like a cop out because that's how it's been used. And in the reality of things, toys get taken away when we can't responsibly use them. For the large majority of people that's all an AR-15 is, an expensive toy. If we can't treat them seriously then the kids are going to grow up to repeal the 2nd amendment and ban all civilian guns. We've had them running duck and cover style drills for most of their lives and that's coming home to roost.

So rather than throw this off on the traditional cop out, even if we admit it's been used that way, we need to figure something out if we want to still have a 2nd amendment in 10-20 years. And I think the two best ways to do that are to define a low capacity rifle with internal magazine as the militia weapon we can have personally or to treat rifles with external magazines as military rifles that live in lock up until your scheduled range day or training weekend with a local reserve unit.