Robert Wright proposes limiting firearms to six bullets and banning detachable magazines.
The sort of law I'm describing would make lots of current guns illegal. (I actually own one.) So you'd have to phase the law in over a couple of years, and, to overcome political resistance, you might have to compensate gun owners for surrendering newly illegal guns--or for having them altered to comply with the law. And, even then, the resistance would be very, very strong. It might even turn out to be insurmountable. But if the question is "What could we do that would greatly reduce the scale of mass killings while preserving the right of Americans to use firearms for legitimate purposes," this, it seems to me, is a real answer.
I don't see how such a law could possibly be implemented absent a massive scaling up of the Bureau of Alcohol, Tobacco and Firearms. Wright explicitly acknowledges this fact, yet proclaims it a "real answer." Well here's an answer that's even more real: there will be less firearm violence if we confiscate every firearm in the United States, but such a situation will never happen.
Wright seeks to find a definite answer for a problem we - absent creating a prohibition-like program - aren't certain can be solved. Sometimes the wisest choice is recognizing that we won't find the "real answer." There are hundreds of millions of guns in civilian possession in America. That is unlikely to change. Policy must start from there. Go.