So... MY access to guns in Podunk USA should be restricted because outlaws in Chicago misuse guns bought elsewhere?
Sorry, I never agreed with the idea of punishing the innocent along with the guilty.
You ask a very key question and its importance should not be dismissed. Having followed this debate for most of my life, it is obvious that there is a difference in perspective between Americans who see themselves first as Americans belonging to a country with one culture, one set of laws, and one main direction that needs to be adopted in approaching a major problem. Then we have people who are more focused on their local area or state. In the old days of the 1800's that was called SECTIONALISM and it severely divided the country over issues like the tariff and slavery. These people want more emphasis on the local powers of government and far less on the national.
So your question reveals much about the way one is oriented when they give their answer.
Lets look at what you asked about restricting guns in Podunk because of the problem in Chicago. On the surface, the first answer would be NO. It is nor fair or right or even practical to impose a system on Podunk which is designed to abate a problem in Chicago when Podunk does not have this problem. If one person a year is murdered by gun in Podunk while 500 are in Chicago - it is obvious that the same solution would not fit both.
However, we then have to face the fact that there are Chicago's all over our nation and a huge chunk of the population lives in them. Of course, the same is true for Podunk. We also have to face the fact that people move around quite a bit, travel quite a bit, commute through our Chicago's and Podunks sometime on a daily basis. Can we practically have two different America's with two different sets of law and culture and approaches to firearms that will work for the nation?
In the 1800's it was easy to think of yourself as a New Hampshire man since you were most likely to die in the same area where you were born. Your entire attitude about politics, economics and culture was built around New Hampshire and its unique environment. What was good for South Carolina might well be poison to New Hampshire and vice versa.
But today one is born in Manchester NH, goes to college in Ohio, gets a job in Oregon, marries someone born in Michigan, has a time share in Florida, gets a later job in Missouri, and then retires to Arizona.
They simply will NOT have those same sectional state based emotions that existed in the 1800's or even the first half of the 20th century.
I do not think there is a 100% foolproof answer on this but the question posed by Goshin is worth exploring and I believe will reveal much more wisdom then if there is a magic number for a magazine capacity.